Captured al Qaeda operations chief Khalid Sheik Mohammed has told interrogators that his organization had plans to attack the Metrorail system in Washington, possibly by igniting a fire, according to law enforcement officials.

Law enforcement and intelligence sources said that Mohammed, the self-described architect of the Sept. 11, 2001, terrorist attacks, provided vague information about the plot along with plans to attack other U.S. targets at home and abroad, including the U.S. Capitol, and the Israeli Embassy in Washington.

During interrogation sessions conducted after his March 1 capture in Pakistan, Mohammed did not provide details about a terrorist strike on the Metro system, and authorities have been unable to determine whether there is any credible threat to mass transit here, two U.S. officials said yesterday.

They cautioned that although Mohammed appears to be cooperating, he may be trying to mislead officials. He and other detainees may be providing false information to cause panic, misdirect intelligence agencies or curry favor with captors without actually giving up any secrets, they said.

Two law enforcement sources said the attack on Metro would have involved a fire or firebombing. One said the Capitol Hill area was a likely target. News of the plot was first reported Monday in the Washington Times.

Mohammed, the most important al Qaeda leader captured to date, was turned over to the CIA after his arrest. U.S. officials have said he has provided some specific information in recent weeks that has been confirmed or shown to be credible.

The FBI has been following up on names and phone numbers found on his computer and among his possessions, including some people suspected of being in the United States, officials have said.

Van Harp, head of the FBI's Washington field office, said any information coming from Mohammed is classified. In general, he said, "any intelligence relative to any threats from any detainees we're taking very seriously and responding."

Transit Police Chief Polly Hanson said yesterday that she could not comment on whether there was a specific threat against Metro.

Hanson said transit system police, like other law enforcement agencies in the region, received a warning from the FBI several weeks ago about "people with incendiary devices." But she added that it was not directed specifically at Metro and mirrored warnings issued several times since the Sept. 11 attacks.

Hanson said Metro has taken steps to increase security in response to the heightened terror alert, including making announcements warning passengers of abandoned packages and having more employees patrol stations and platforms. Hanson said a "sweep team" of three officers and an explosives-detection dog regularly patrols rail stations, particularly those near "federal assets" deemed potential targets.

Officials have said that Mohammed has told interrogators that al Qaeda operatives discussed many potential plots, including bombing apartment buildings, Jewish organizations and other "soft targets" that have been included in FBI warnings to law enforcement agencies. Other detainees have talked about strikes against subway systems in New York and elsewhere.

"All of the usual targets are mentioned by him, but it's hard to know if that's because they're all the usual targets or if there's more to it than that," said one U.S. intelligence official.

Officials in Europe have uncovered several suspected al Qaeda terror plots against subway systems. Eight men were arrested last fall as part of an alleged plot to release poison gas on the London Underground, while French authorities this year discovered a vial with traces of the poison ricin at a Paris rail station.

Law enforcement sources differed over whether a Metrorail plan was or could still be in the making.

One source said it appeared that the Metrorail threat, along with the threat against other potential targets Mohammed mentioned, diminished somewhat with his capture. But another said that might only be wishful thinking.

D.C. Police Chief Charles H. Ramsey said he has not been notified of any specific threats and was only "aware of threats of a more general nature." One senior federal official said, "We don't give it much credence."

Staff writers Jerry Markon, Susan Schmidt and Katherine Shaver contributed to this report.