DETROIT (Reuters) - Bomb threats against three U.S. passenger jets and two Amtrak trains triggered extensive security checks on Tuesday but no explosives were found, authorities said.
Security officials, aided in some cases by sniffer dogs, took hours to sweep through the planes operated by Northwest Airlines . But the searches, of passengers and luggage as well as the airliners themselves, ended without incident.
"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 screened by federal officials and airline staff. Both eventually departed for their respective destinations, Northwest said.
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."
There were also bomb threats against two Amtrak trains traveling 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, said Amtrak spokesman Dan Stessel.