20091227

WASHINGTON (Reuters) - There are no signs that the incident in which a Nigerian man has been charged with trying to blow up a U.S. passenger jet bound from Amsterdam to Detroit was part of a larger plot, a senior U.S. official said on Sunday.

"Well, right now we have no indication that it is part of anything larger. But obviously the investigation continues. And we have instituted more screening and what we call mitigation measures at airports," U.S. homeland security chief Janet Napolitano told CNN's "State of the Union" program.

Napolitano also said there was "no suggestion" that authorities in Amsterdam had improperly screened the man, Umar Farouk Abdulmutallab. She added that there was no "specific" or "credible" information to move him to a more stringent screening list.

The suspect was overpowered by passengers and crew on the Delta Air Lines plane from Amsterdam on Christmas Day.