On Sept. 1, as patients sweltered in hospitals without power and thousands of people remained stranded on rooftops and in attics, crucial rescue efforts were delayed as word of such attacks spread.

But more than a month later, representatives from the Air Force, Coast Guard, Department of Homeland Security and Louisiana Air National Guard say they have yet to confirm a single incident of gunfire at helicopters.

Likewise, members of several rescue crews who were told to halt operations say there is no evidence they were under fire.

To be sure, the streets of New Orleans posed real dangers in the days following Katrina. Many rescue workers said they heard gunfire; one doctor reports that shots came close enough to Charity Hospital that he heard the bullets hit.

But so many rumors were swirling that the facts still haven't been sorted out. A picture is emerging of heroic but harried rescue workers from dozens of organizations forced to make snap decisions with only slender threads of information and no reliable communications.

The storm created so much confusion that government officials cannot even agree on whether they ever issued an order to halt flights or other rescue efforts.

Sometimes the mere rumor that they had was enough.

On the morning of Sept. 1, Mike Sonnier was directing rescue helicopters at his company, Acadian Ambulance, when one of his pilots called to say the military had suspended flights after gunfire was reported in the air near the Louisiana Superdome.

Should he continue rescuing sick evacuees, leaving his pilots and medics at risk - or suspend his company's flights?

Sonnier immediately shut down flights.

"Until I can confirm that this did happen or didn't happen, it's not a chance that I can take," he said.

Sonnier said that when he checked with the National Guard about two hours later, he was told it was OK to fly. At that point Acadian resumed operations. Even today, it's not clear whether a military order to stop flying was ever actually made.

Reports persisted throughout the day of helicopters in the cross hairs, part of the image of a city under siege that was spreading across the nation.

"Hospitals are trying to evacuate," a Coast Guard spokeswoman at the city emergency operations center told The Associated Press. "At every one of them, there are reports that as the helicopters come in, people are shooting at them."

But that initial report proved hard to confirm. Two Coast Guard spokesmen who were asked in recent days about helicopter shootings said there were no incidents of any Coast Guard personnel or vehicles taking fire.

"We don't know of any shots ever fired directly at us," said Capt. Bob Mueller, commander of the Guard's New Orleans station. "But there were a number of reports of shots fired in the air. There were two occasions where all helos were directed to land. I believe those orders came from the Superdome. Our flatboats did stand down Sept. 1."

Lt. Pete Schneider, a spokesman for the National Guard, which was handling Superdome evacuations, said it was a civilian who told guardsmen in the area that shots had been fired. Schneider said flights continued despite the danger.

But a spokesperson for the Department of Homeland Security - which oversees the Federal Emergency Management Agency - contradicted that statement, saying Superdome flights were temporarily suspended because of gunfire.

The confusion affected more than just helicopter crews. Florida Task Force 1 was using boats to reach the stranded - but not on Sept. 1.

Because of reports of gunfire, a FEMA support team ordered the Florida task force to stop work for the entire day unless law enforcement protection could be found, task force leader Dave Downey said. That help never came. Meanwhile, thousands of people were stuck in attics and on roofs of flooded houses in New Orleans.

"We had just had a very successful day before," when they rescued 400 people, said Downey, whose crew manned boats. "It definitely slowed down our rescue efforts. ...

"In a rescue scenario, every hour that slips by makes the situation more complicated, and the chance for survival diminishes," he said.

Other teams also were ordered to stand down. Many suspensions were for a matter of hours, and in some cases rescue teams simply moved to areas thought safe and continued to work.

FEMA sent mixed messages in recent days on whether rescue efforts were placed on hold.

"If, on the ground, if they were in middle of a search and they were being shot at, for safety reasons, they may have temporarily put that search on hold," said Deborah Wing, a FEMA spokeswoman in Washington. Later, she said by e-mail that no operations were ever suspended, despite "reports of gunfire."

Some who were in New Orleans that day described moments of real peril. Tyler Curiel, cancer doctor at Tulane University Hospital, said a sniper shot at him and his military escorts in the street as they evacuated patients from Tulane and Charity hospitals. Curiel said the gunman was in a nearby parking deck shooting at Charity's emergency room about noon Sept. 1.

"You could hear the shots fired, you could hear the bullets hitting," he said. "I just had to duck."

And Charity Hospital executive Ed Burke said he saw a sniper fire a shot at the emergency room from a parking garage the day before.

Many other stories don't pan out. Reports that an employee of the Louisiana Department of Wildlife and Fisheries was shot during a rescue mission were false, a department spokesman said. And although one man was arrested for shooting a .22-caliber rifle in the air as a helicopter flew by, it occurred several days after the major rescue operations at hospitals and the Superdome.

Tales of snipers shooting at helicopters and rescue personnel were among many tales of violence that swirled around New Orleans in the initial days after Katrina. Accounts of murders and rapes in the Superdome and convention center have since been called into question by state and local authorities.

Consider how the helicopter shooting stories morphed during one day of news coverage.

Early the morning of Sept. 1, National Public Radio reported that a Chinook helicopter was shot at. That afternoon, NPR reported that search-and-rescue teams had been shot at. By 5 p.m. on Fox, the Chinook had become a Sikorsky. That evening, Keith Olbermann, host of MSNBC's "Countdown," opened the show talking about "an unknown number of residents shooting at and threatening the very people trying to save them."

By the next night, U.S. Rep. Charlie Melancon, D-La., in an MSNBC interview with Tucker Carlson, said matter-of-factly that bus drivers and helicopters were being shot at.

Perhaps one of the best examples of the feedback loop created by rumor and amplified by the media happened at Acadian Ambulance.

On Wednesday, Aug. 31, an Acadian medic reported that he had been unable to drop supplies at a hospital in suburban Kenner because of armed crowds on the roof. But the medic never went to the hospital, turning back after hearing a warning over military radio.

Acadian Chief Executive Richard Zuschlag repeated the story to the media, unaware that his crew had been acting on a military radio report. Zuschlag said he learned only in the past week that his crew had not actually seen the crowds.

"There are probably half a dozen incidents like that, when you really try to get to the bottom of it," he said. "It's A talking to B talking to C talking to D. But when A talks to D, it turns out it wasn't really that way."

A spokesperson for Kenner Regional Medical Center said on Sunday, Oct. 2, that she knew of no such incident.

Acadian pilot Marc Creswell believes the sound of gunfire from thugs roaming the streets gave rise to the widespread tales of rescue workers being targeted.

"You have to understand, there's a lack of communication, the hostile nature of the crowd, the people looting, shooting at people," Creswell said. "The next person passes on and says they shot five people. ...

"Before you know it, that turns into platoons of people that were shooting, and there's just no way to verify those things, and people got really scared. Was there some embellishment? Maybe so."

The debate about what actually happened isn't over. The Department of Homeland Security plans to investigate whether helicopters were targeted, as well as the extent to which rescue operations were delayed. The department hopes, according to a spokeswoman, "to achieve clarity on this issue."

One month later, Downey, of Florida Task Force 1, isn't sure the decision to halt operations was the right one.

"In hindsight, it didn't appear as though security was as big an issue. But (at the time) we were inundated with reports from back home, saying the situation was very violent. We didn't know what to believe.

"You've heard of the `fog of war' - well, in the fog of disaster response, sometimes information is sketchy, and you have to act on the information you have available at that time."