WASHINGTON - One Metro transit train smashed into the rear of another at the height of Washington's evening rush hour yesterday, killing at least six people and injuring scores of others as cars of the trailing train jackknifed into the air and fell atop the first.

District of Columbia Fire Department spokesman Alan Etter said crews were cutting apart the trains to get people out in what he described as a "mass casualty event."

Rescue workers propped ladders up to the upper train cars to help survivors escape. Seats from the smashed cars had spilled out onto the track.

Fire Chief Dennis Rubin said rescue workers had treated 70 people at the scene and sent some of them to local hospitals, two with life-threatening injuries. A Metro official said the dead included the female operator of the trailing train. Her name was not immediately released.

The crash about 5 p.m. took place on the system's red line, Metro's busiest, which runs below ground for much of its length but is at ground level at the site near the Maryland border.

Metro chief John Cato said the first train was stopped, waiting for another to clear the station ahead, when the trailing train plowed into it. Officials had no explanation for the accident.

Homeland Security Department spokeswoman Amy Kudwa said that federal authorities had no indication of any terrorism connection. *