A newly released U.S. diplomatic cable discloses the existence of previously undisclosed participants in the Sept. 11, 2001, plot: a group of Qatari men who conducted surveillance of targets in New York and the Washington area before leaving the United States on the eve of the attacks.

The three men flew into the United States on Aug. 15, 2001, and "visited the World Trade Center, the Statue of Liberty, the White House, and various areas in Virginia" before flying on to Los Angeles, according to the cable, part of the cache of documents obtained by the antisecrecy group WikiLeaks.

But a U.S. official, speaking on the condition of anonymity in order to comment on classified material made public by WikiLeaks, said that the three men were "looked at" within days of the attacks and that investigators concluded they could not be charged.

"There is no manhunt," said the official, playing down a report in Britain's Daily Telegraph newspaper that disclosed the contents of the cable. "There is no active case. They were looked at, but it washed out."

The cable, sent on Feb. 11, 2010, from the U.S. Embassy in Doha, Qatar, to various agencies in Washington, including the FBI and the CIA, recommended that an individual named Mohamed al-Mansoori be added to a government watch list. The cable said he was a threat to civil aviation in the United States and abroad.

The cable goes on to explain that Mansoori assisted the group of three Qataris - identified as Meshal Alhajri, Fahad Abdulla and Ali Alfehaid - while they were in the United States.

Mansoori, from the United Arab Emirates, lived in Long Beach, Calif., in September 2001. "He is suspected of aiding people who entered the U.S. before the attacks to conduct surveillance of possible targets and providing other support to the hijackers," the cable states.

The existence of a surveillance team supporting the 19 hijackers led by Mohammed Atta appears to add a new element to the narrative of the plot's execution. There is no direct mention in the 9/11 Commission report of such a team.

Two of the hijackers, Nawaf al-Hazmi and Khalid al-Mihdhar, first landed in Los Angeles, and the report says it is likely they would have had some "friendly contacts" in California. Khalid Sheik Mohammed, the self-proclaimed mastermind of the 9/11 attacks, denied that al-Qaeda had any operatives in the state, according to the commission's report.

The report also notes that there was evidence that a second wave of attacks was being prepared. Philip Zelikow, a member of the commission, said that this group of Qataris might have figured in such a plan. He noted that by the time the Qataris reached the United States in August 2001, the 9/11 plan was largely in place, so surveillance by such late arrivals appears odd.

"Not everything is in the report, and my memory of the details has dulled with time so I can't say if we had some trace of this group," Zelikow said. "They might have been seen by us as a group that was part of a second wave, and if that was the case, we wouldn't have named them for obvious reasons."

The three Qataris are part of a 2002 FBI list of individuals whom the government wanted to interview about the Sept. 11 attacks.

After leaving the East Coast, the three men stayed at a hotel near the airport in Los Angeles. The cable says the hotel rooms and the men's plane tickets were paid for by a convicted terrorist, who was not named in the document. The three men also spent a week traveling around California with Mansoori.

Hotel staff later told investigators that the men had "pilot-type" uniforms and computer printouts listing pilot names, airlines, flight numbers and flight times.

The men were scheduled to fly to Washington on Sept. 10, 2001, on the Boeing plane that was hijacked the next day and flown into the Pentagon. Instead, the men flew to London and then on to Qatar on Sept. 13.

Mansoori's visa was later revoked and he was apparently able to leave the United States unhindered.

The CIA and the FBI declined to comment on the cable.

finnp@washpost.com tatej@washpost.com