Bomb threats against three US passenger jets and two Amtrak trains have triggered extensive security searches but have uncovered nothing suspicious.
Security officials, aided in some cases by sniffer dogs, took hours last night to search the planes operated by Northwest Airlines. But the searches, of passengers and luggage as well as the airliners themselves, uncovered nothing.
"Fortunately these threats turned out not to be credible," said Yolanda Clark of the Transportation Security Administration.
The aircraft included one that arrived at Detroit's Metropolitan Airport on a flight from Miami, according to Clark and a spokeswoman for Northwest.
The second and third flights, from Memphis to Miami and Los Angeles to Detroit, were grounded before takeoff and searched by Northwest and federal officials.
Both Clark and Northwest spokeswoman Mary Stanik said they were unable to comment on the source of the bomb threats but Clark stressed that authorities took "all of the precautions necessary to rule out any possible real threats."
The aircraft due to make the Northwest flight to Detroit from Los Angeles had still not been cleared for takeoff hours after the bomb threats were received, according to Clark. Stanik said she was unable to offer immediate comment on the status of the flight.
There were also bomb threats against two Amtrak trains travelling between New York and Miami.
A spokesman for the railroad said more than 140 passengers were taken off the northbound Palmetto at the Selma-Smithfield station in North Carolina and the train was searched. Service resumed after a delay of nearly 2 1/2 hours.
At roughly the same time, 176 passengers were evacuated from the Silver Meteor in Philadelphia. Service resumed after a 45-minute delay.
Nothing was found on either train, Amtrak spokesman Dan Stessel said.