WASHINGTON (CNN) --
U.S. officials say investigators would like to talk to people who did not show up for the postponed Air France flights -- and are still interested in 13 passengers who were interviewed by French authorities.
A senior U.S. counter-terrorism source says investigators are "actively interested" in questioning some of those who did not show up.
French sources have told CNN they believe the names of all 13 -- interviewed by French law enforcement -- were on U.S. terror watch lists. American authorities have not confirmed that, but one senior U.S. counterterrorism official tells CNN that most of the names of those interviewed and those of interest who did not show up for their flights were on watch lists.
This official says some of the passenger names were not previously on watch lists but came up in recent intelligence.
A U.S. official told CNN on Thursday that one of those who did not arrive for his flight had a commercial pilot's license.
Officials say they still believe there is a real possibility of some type of terror attack aimed at the United States. As one counterterrorism official put it, authorities do not believe the "threat window" has closed. There is concern not only about a plot involving aviation but also about other modes of attack as well, including one using a so-called "dirty bomb," a device that spreads radiological debris.
As for a mention in The Washington Post about Las Vegas being a possible target of a hijacking from Paris, several officials call that only an analytical theory as they look at the possible route of a Paris-Los Angeles flight. Concern has been expressed recently about Las Vegas being the target of a terrorist attack.
U.S. Homeland Security Director Tom Ridge, meanwhile, said he was "relieved" that Christmas had passed without a terrorist attack.
Nevertheless, he said, the threat has not diminished. "We are still at that same level of risk," Ridge told CNN on Friday. (Full story)
Attention to Mexico
Officials say Mexico worries them, too. One government source said there is concern not just because of the country's proximity to the United States, but also because there is a "credible threat related to Mexico."
Another senior administration official said that the United States is "in regular touch with Mexico" on the current threat.
"There is credible information which we take very seriously showing a threat related to a number of places of concern, and Mexico is one of them," the official said.
This official said that Mexico has implemented a number of security measures requested by the United States, but did not preclude further measures being asked of Mexico.
"We have an open channel," the official said. "As we get information we act on it and pass it to Mexico. It is an ongoing dialogue."
Officials say the threat is within the context of the larger volume of information the U.S. government is receiving that indicates al Qaeda is hoping to use an airplane originating outside the U.S. as a weapon.
Officials said the U.S. continues to press other countries -- beyond Mexico and France -- to step up security. But officials declined to name those other countries.
Flights delayed Friday
Two Air France flights from Paris to Los Angeles were delayed Friday because of more thorough screening of all bags and passengers, a U.S. aviation official told CNN.
When those flights land, they will be handled by airport crews remotely, with passengers screened off the tarmac and bused into the terminal, the official said.
This official also said that select flights Friday to Los Angeles from other countries will be handled in a similar fashion.
French authorities: Passengers questioned
Meanwhile, the French Foreign Ministry said all passengers from Wednesday's canceled Air France flights to Los Angeles have been questioned.
A spokesman said 13 passengers were questioned by police. All others were questioned by airport security.
All were sent home, the ministry said, adding there will be no official investigation or follow-up.
Air France said its fights were resuming Friday.
France agreed to cancel all Air France flights between Paris and Los Angeles Wednesday and Thursday over security concerns expressed by U.S. officials.
A government source told CNN Thursday the United States had intelligence that one of the six canceled Air France flights might be targeted by terrorists during the Christmas holiday period.
He could not describe what the intelligence said specifically about the threat that officials believed may have been posed by passengers or crew.
U.S. intelligence officials told their French counterparts that members of the al Qaeda terrorist network would try to board the planes over Christmas, said a French judicial official, speaking on condition of anonymity, The Associated Press reported.
Wednesday's Air France flights 68 and 70 from Paris to Los Angeles and Thursday's flight 68 to Los Angeles were grounded. Three other Los Angeles Air France flights were canceled because the planes remained in Paris and couldn't continue to their final destinations.
http://www.cnn.com/2003/WORLD/europe/12/26/threat.level/index.html