FALL RIVER, Wis. (AP) _ An Amtrak passenger train that derailed, killing one person and injuring 33, was going too fast as it was switched from one track to another, a railroad official said Friday.

The accident occurred as the Empire Builder, a Seattle-to-Chicago train carrying 231 Amtrak passengers and dozens of others riding in private cars, was being switched from one set of Soo Line tracks to a parallel set.

''The only thing we've determined is that it went through (the switch) at too high a speed,'' Robert Schive, a Soo Line division superintendent, said. A train normally slows to about 25 mph when switching from one track to another, he said.

A source close to the investigation, who spoke on condition his name not be used, told The Associated Press the train's crew hadn't been told it would be switched in Fall River, and so approached the switch too quickly. Construction made the switch necessary.

National Transportation Safety Board staff members were meeting in Madison Friday to discuss their findings, and a spokesman said he couldn't confirm the source's statement.

''We just don't have the facts nailed down on that,'' said Bill Bush.

Bush did confirm the maximum safe speed for changing tracks was 10 mph and said investigators hoped to pinpoint within days the train's speed at the time of the derailment.

Walter Day, 49, of Waupun, Wis., was killed when the lead locomotive of the 15-car train plummeted 20 feet down an embankment and was half buried in a marsh. Columbia County Coroner Kenneth Ruehl said the cab was filled with mud, in which Day, a fireman for the Soo Line, was buried.

Thirty-three other people were treated at hospitals. One passenger and three Soo Line employees were admitted.

Amtrak officials, who said Thursday the train carried 321 passengers and crew, later said they could not be sure of the total because of uncertainty over the number of people aboard the private cars.

Several passengers on board the train estimated it was travelling 60 to 70 mph when the derailment occurred, but Schive said that seemed ''a little high.''

Soo Line trainmaster Michael Duffert said the train may have been going 35 or 40 mph.

The coroner took custody of the tape from a speed recorder aboard the Amtrak locomotive, and said he would turn it over to the NTSB.

Pat Campion of St. Paul, Minn., a passenger in one of five private cars at the end of the train, said the train seemed to be going too fast to negotiate the switch.

''I just felt like we went from 70 miles an hour to zero in a second,'' said Amtrak passenger Russell Martins of Twisp, Wash. ''I closed my eyes and prayed.''

''It was all over in a matter of 15 seconds,'' passenger Luckie Hotaling of Westfield, Wis., said. ''Nobody panicked, nobody screamed, everybody was great.''

None of the private cars, which were carrying railroad buffs to a convention in Milwaukee, crossed the switch, and none of them derailed. They resumed their rail journey Thursday night via an alternate route, while Amtrak passengers were bused to Milwaukee.

Repair crews Thursday night returned most of the Amtrak coaches to the tracks, and Friday they were busy repairing damaged track and preparing to lift the overturned locomotives out of the swamp.