At least three people were killed and about 100 others were taken to hospital when a passenger train traveling on a new route derailed Monday in Washington state, police said.

"There are a lot of critical injuries and so we won't know until we get updates from the hospital," Washington State Police spokeswoman Brooke Bova told reporters as she gave the toll, when asked about whether there would be more victims.

The train, which was carrying 77 passengers and seven crew members, state police said in an update on the situation. 

It derailed in DuPont about halfway between Tacoma and the state capital Olympia on a curve that passes over busy Interstate 5 at about 7:40 am (1540 GMT).

All but one of the train's 14 rail cars jumped tracks, plunging off a bridge onto a busy highway, where they hit five motor vehicles and two trucks, police said