HYDER, Ariz. (AP) _ An Amtrak train carrying 268 people derailed in the rugged Arizona desert early today after someone tampered with the tracks, and the sheriff said domestic terrorists may have been responsible. A crew member was killed and about 100 people were injured when four cars plunged 30 feet into a dry streambed.

Notes found outside the derailed train were signed ``Sons of Gestapo,'' Maricopa County Sheriff Joe Arpaio said.

Amtrak's Sunset Limited was bound for Los Angeles from Miami and was carrying 248 passengers and 20 crew members when it derailed sometime between 1 a.m. and 1:30 a.m.

Deputies found a one- or two-page message signed ``Sons of Gestapo,'' at the scene, the sheriff said. The note referred to the government sieges at Waco, Texas, and Ruby Ridge, Idaho, frequent rallying points for anti-government groups.

``That's what leads me to believe this is a terrorist attack,'' Arpaio said.

In Washington, Amtrak President Thomas M. Downs said the crash happened on a little-used section of track that had not had a train pass by in 18 hours. ``It was a unique incident ... it does not appear to be an accident.''

Downs said a 36-inch steel bar weighing about 18 pounds that is used to connect two 39-foot sections of rail had been removed, with wire installed over the gap to keep a warning system from sensing the missing connection and alerting the crew.

Officials said the bar could have been removed and the wire installed in about 10 minutes by someone with rudimentary knowledge of the safety system.

``I find it despicable that anyone would jeopardize the lives of Amtrak passengers and crew for any reason whatsoever,'' Downs said.

Separately, an Amtrak employee being treated in a Phoenix hospital said he turned over an anti-government manifesto of some sort to sheriff's deputies.

Roberto Concepcion, 48, who worked as a bartender on the train, said that while he was helping people after the crash, a passenger came up to him and gave him a single piece of typewritten paper the passenger said he found on the tracks.

``He said it was an unsigned, typewritten, anti-government manifesto. It was anti-ATF, anti-FBI and anti-government,'' Concepcion said. ATF is the federal Bureau of Alcohol, Tobacco and Firearms.

Concepcion said he gave the paper to someone from the sheriff's department without reading it. Arpaio wouldn't comment on Concepcion's story.

The Phoenix FBI office was closed for the Columbus Day holiday and calls were referred to a spokesman at the scene who wasn't immediately available. FBI agents were on the scene, along with investigators from the National Transportation Safety Board and other agencies.

One person was killed, 12 were seriously hurt and about 100 others suffered less serious injuries, said Sgt. Tim Campbell, a sheriff's spokesman. Downs identified the dead victim as Mitchell Bates, 41, a sleeping-car attendant based in Los Angeles.

Two sleeper cars and a diner plunged off the bridge. In all, both locomotives and the first eight of the train's 12 cars derailed, Amtrak said.

Joyce Matthews, 49, of British Columbia, was on her way to Disneyland with her 24-year-old daughter. She was asleep when the train derailed.

``There was a loud roar and everything was shaking. It was beginning to tilt and then everything just shook and stopped,'' Matthews said.

``I heard babies screaming and their mother was hollering each one of their names, one after the other,'' said Betty Addington, 60, of Dallas, who was traveling with her 80-year-old mother.

Arpaio said two people spotted by a helicopter crew three miles from the scene were questioned, but he didn't believe they had anything to do with the wreck. They were being interviewed by the FBI later.

An engineer had reported seeing something unusual, Campbell said without elaborating.

A ``black box'' that records the train's speed, acceleration and other details was recovered, but had not yet been read, said Jon Poston, spokesman for the Arizona Corporation Commission, which regulates railroads. Investigators didn't immediately find any equipment problems with the train, he said.

The remote crash site was accessible only by four-wheel-drive vehicles. The rescue was carried out almost entirely by air.

It appeared the locomotives had made it across the bridge when the derailment occurred.

The train sat with the engines upright, one car behind them tilting toward the streambed and the next three cars lying in the bed, with little visible damage. The remaining cars sat upright on the far side of the streambed.

Brian Hamblet of Los Angeles compared the experience to the earthquake that struck his city in January 1994 _ ``only we were falling 25 feet through the air. The whole thing happened like in slow motion. It was like taking a roller coaster ride.''

A triage center was set up on sandy desert soil next to a dirt road about six miles from the accident scene. Medical personnel in lab coats bustled alongside military units in camouflage as helicopters landed nearby with injured passengers. A fire truck sprayed the landing pad with water in in an attempt to control dust whipped up by the choppers.

``We've got helicopters from all over the state, including the military. They're bringing all the patients out to the landing zone, where they're being transferred to various ambulances,'' Campbell said.

A train was sent from Phoenix to bring back the uninjured passengers.

In Phoenix, hospitals reported treating at least 40 including one woman who was listed in critical condition. Among the hospitalized: a 3-month-old boy, and a 31-year-old woman who was on her honeymoon.

Other passengers were treated at the scene.

In Los Angeles, James Hall wept as he said he learned of the derailment when he went to Union Station to pick up his mother, who was traveling there from Mississippi to undergo an operation. ``I'm just hoping for the best, hoping she's all right,'' Hall said.

The accident site is 27 miles east of this small town in Yuma County and about 20 miles north of Interstate 8, which runs through southwest Arizona.

The train left Miami on Friday, but because of Hurricane Opal, the section of the journey from Jacksonville, Fla., to New Orleans was made by bus rather than by train, said railroad spokesman Stephen Taubenkibel. The regular route, about 3,000 miles, passes through Florida, Alabama, Mississippi, Louisiana, Texas, New Mexico and Arizona on way to California.

Two years ago, an eastbound Sunset Limited train derailed into a bayou near Saraland, Ala., killing 47 people. It was the worst accident in Amtrak's quarter-century history. An investigation found that a barge lost in fog had struck the bridge shortly before the derailment, knocking the rails out of alignment.