'Credible Threat' To NYC Subways

City officials stepped up mass transit security Thursday, saying they had received a credible threat that New York's subway system could be the target of a terrorist attack in coming days. But Homeland Security officials in Washington downplayed the threat, saying it was of "doubtful credibility."

Mayor Michael Bloomberg said the threat originated overseas, and was the most specific terrorist threat city officials had received to date. No one in New York has been arrested or detained, he said.

CBS News correspondent Randall Pinkston reports that while Bloomberg and Kelly said they would take the subway home tonight, a source tells CBS News that the matter may not be so trivial.

According to the source, the information came with specific details about how the attack would be mounted, how many people might be involved, and by what route the terrorists would approach the rail system.

CBS News correspondent Jim Stewart reports that the threat was picked up in chatter on the Internet.

"The people involved, approximately 19 or so, went into great detail how they might carry out this attack," Stewart said. "They talked about placing themselves as suicide bombers on the New York subway system using backpacks and briefcases — specifically using baby carriages."

But in Washington, Homeland Security Department spokesman Russ Knocke said "the intelligence community has concluded this information to be of doubtful credibility. We shared this information early on with state and local authorities in New York." Knocke did not elaborate.

A counterterror official, who was briefed about the threat by Homeland Security authorities, said the intelligence was considered doubtful because it did not reflect "on-the-ground, detailed" information. Rather, the official, who also insisted on anonymity, said the intelligence was similar to "what can be found on the Internet and a map of New York City."

Stewart reports that different branches of government are not regarding the threat with the same amount of gravity.

"Tomorrow, you will hear how this threat is perceived differently by the F.B.I. and the Department of Homeland Security, the C.I.A., the New York City Police Department. They all see it through a different prism."

Sen. Charles Schumer, D-N.Y., said he had spoken with Washington authorities, and the threat did not have the highest level of credibility or corroboration.

"Nonetheless, in a post 9/11 world you cannot be too careful," he said.

New York Police Commissioner Ray Kelly urged the public to report suspicious people or activities. Police planned to look through bags, briefcases, baby strollers and luggage in a large-scale search of the mass transit system.

"We have done and will continue to do everything we can to protect this city," Bloomberg said, adding that he planned to take the subway home Thursday night. "We will spare no resource, we will spare no expense. We have increased our police presence on our subways."

Some commuters took the threat in stride.

Paul Radtke, 45, of Hoboken, N.J., said he had heard similar warnings before and found it hard to take them all seriously.

"Unless it's something dramatic that's happening, I've got to go to work," Radtke said after getting off a subway train at Penn Station. He said the only travel habit he is changing is trying not to make eye contact with police officers so they won't search his bag.

An estimated 4.5 million passengers ride the New York subway on an average weekday. The system has more than 468 subway stations.

New York's security level remained at orange, the second-highest. The level has stayed the same since Sept. 11.

Bloomberg said there was no indication the threat was linked to this month's Jewish holidays.

"We have never had before a specific threat to our subway system," he said. "Its importance was enhanced above the normal level by the detail that was available to us from intelligence sources."

Meanwhile, CBS News correspondent John Roberts reports that President Bush said today that 10 al Qaida plots had been thwarted, and three of those targets were in the United States.