OPA-LOCKA, Fla. (AP) _ Investigators believe vandals wedged two pipes under the tracks, causing an Amtrak locomotive and four passenger cars to derail. Six passengers suffered minor injuries.

Amtrak's 10-car Silver Meteor was traveling from New York to Miami with 57 passengers and 17 crew members Friday night when the accident occurred.

The pipes were placed between rail switches, where the line splits in different directions, said Clyde Tucker of the operations center for CSX Transportation, which maintains the tracks.

''Vandals, that's the report I'm getting,'' he said.

The FBI, National Transportation Safety Board and local police were investigating.

Jimmy Waters, a passenger from North Carolina, said he was playing cards with friends near the rear of the train when the accident occurred.

''We just heard the funny noises. It started jerking, and then somebody said, 'Everybody get off the train,''' he said.

The engineer, assistant engineer and four passengers were taken to Parkway Regional Medical Center, where they were in stable condition, said spokeswoman Linda Harn. One of the injured was a teen-ager.

The train was traveling through a 45-mph zone when it derailed, and there was no indication it was speeding, said CSX spokesman Gary Cease. It was just a few miles from its final stop at the Miami suburb of Hialeah.

The derailment was the second Amtrak accident in three months in south Florida. Six people were killed March 17 in Fort Lauderdale when an Amtrak train collided with a gasoline tanker truck at a crossing.