Amtrak's Seattle-to-Chicago Empire Builder passenger train, barreling along at 70 mph, jumped the tracks near this northern Idaho town early yesterday, injuring about 80 people.

A rail jammed into one car, but missed the passengers, authorities said.

All but the last car of the 12-car train left the tracks around 2:15 a.m., and six coaches, two baggage and crew cars and both locomotives overturned onto their sides, said Howard Kallio, spokesman for Burlington Northern railroad, on whose tracks it was operating. He said the train was carrying 248 passengers and a crew of 19.

Kallio said the train was traveling at 70 mph at the time of the wreck, within the 79 mph speed limit.

The cause of the derailment was not known, he said.

Seventy-six people went through the emergency room at Bonner General Hospital in Sandpoint, about 16 miles south of the derailment site, and 12 were admitted for observation, said Nursing Supervisor Betty Jo Wood. Hospital officials said the most serious injuries ranged from back or neck pains to broken bones.

Five people went to Bonner's Ferry Community Hospital, about 20 miles north of the derailment, and three were admitted in stable condition, said sheriff's Deputy Gay Walden.