At least two E-mails revealing the purported plot were sent to a select crowd of business and arts executives early last week by New Yorkers who claimed to have close connections to Homeland Security and other federal officials, authorities said.

The NYPD confirmed that it learned of the E-mails on Oct. 3 - three days before Mayor Bloomberg, Police Commissioner Raymond Kelly and the FBI went public with the threat.

"I have just received a most disturbing call from one of my oldest friends from growing up in Washington," one E-mail began. "He called with a very specific caution to not enter or use the New York City subway system from Oct. 7 through 10th."

Cop guards downtown Broad St. subway station Monday as New Yorkers’ nerves are frayed by terror warning.

A second E-mail sounded a similar ominous tone: "As some of you know my father works for Homeland Security, at a very high position and receives security briefings on a daily basis.

"The only information that I can pass on is that everyone should at all costs not ride the subway for the next two weeks in major areas of NYC."

One of the E-mails was dated Oct. 3 with a 6:05 p.m. time stamp, about 90 minutes before Bloomberg was fully briefed on the threat, a police source said.

The early warning infuriated several police officials, who noted that Homeland Security officials had challenged the credibility of the threat after the city and FBI warned the public.

"We're briefing the mayor, ratcheting up security, talking about when to go public - and Homeland Security is downplaying the whole thing while their people are telling friends to stay out of the subways," a police source said. "It's pretty bad."

NYPD investigators obtained copies of the E-mails on Oct. 4, as Bloomberg and Kelly were finalizing a plan to respond to the threat, and police officials gave the E-mails to the Homeland Security Department, police said.

'Members of our corporate security network informed the Police Department of the E-mails' existence days prior to any announcement of the threat," NYPD Deputy Commissioner Paul Browne said yesterday.

Homeland Security officials confirmed that they were told about the early E-mail warnings.

"We have looked into them, but do not consider them to be of great significance," Homeland Security spokesman Russ Knocke said yesterday.

"At best, they were based on anecdotal accounts of very limited information," he added, declining to reveal whether the feds were investigating.

The News obtained copies of two E-mails, one with the foreboding subject line: "Alarming call from Washington." Unsigned versions were also posted on Snopes.com, a site that examines urban legends.

One of the E-mail senders, when reached by The News, declined comment.

The plot, calling for terrorists to detonate bombs hidden in briefcases, suitcases or strollers, has been largely discredited since the public warning.

Bloomberg has defended his response, arguing the city had no choice but to act on the "specific threat." He has said he held off alerting the public until Oct.6 to give authorities time to round up suspects in Iraq.