CIA analysts mistakenly thought they had found secret al-Qaida messages embedded in the crawl on the news channel, but the analysis turned out to be wrong, NBC reported on Monday, citing senior US officials.

According to the report, CIA experts thought they found numbers signalling upcoming attacks hidden in the information that scrolled across the screen.

"Dates and flight numbers, geographic coordinates for targets, including the White House, Seattle's Space Needle, even the tiny town of Tappahanock, Virginia," the report said.

A janitor mops the floor at the headquarters of the Central Intelligence Agency in Langley, Virginia

No comment

NBC said the CIA would neither confirm nor deny the report, but said it is the "agency's job to run all plausible theories to the ground, especially when American lives could be at risk".

NBC said the alleged threats were found through steganalysis, using sophisticated software to analyse images for hidden messages.

Former secretary of Homeland Security Tom Ridge was briefed on the analysis and was asked whether he considered it to be "a little bit bizarre".

"Bizarre, unique, unorthodox, unprecedented. Speaking for myself, I've got to admit to wondering whether or not it was credible," Ridge told NBC.

Unrepentant

Ridge said the possibility of hidden messages could not be discounted, given other intelligence chatter and an attack on Saudi Arabia.

Asked whether in retrospect it was a mistake to raise the alert level based on the analysis, Ridge said, "No."

"We informed a lot of people and we acted accordingly based on our best information and best conclusions and the information that we had at the time."

A CIA spokeswoman referred a call seeking comment to the National Counterterrorism Centre. Spokesmen for the Director of National Intelligence and the Department of Homeland Security could not be reached for comment.