A high-speed Amtrak Acela train plowed into a car at a crossing Wednesday, killing a woman and her 8-year-old grandson and causing major delays along the Boston-to-Washington corridor.

The accident happened around 7:30 a.m., Amtrak (search) spokeswoman Tracy Connell said. The train hit the car and dragged it several hundred yards, with the engine coming to rest on top of the demolished vehicle.

Patricia Metzermacher, 61, and Zachary Joseph Metzermacher were killed, police said. A granddaughter, Courtney Metzermacher, 4, was critically injured.

None of the 116 passengers and four crew members on the train were hurt, police said.

Waterford First Selectman Paul Eccard said witnesses told police the gates at the crossing were working when the accident happened. He said police had not determined how the car got onto the tracks.

Train service was halted for about six hours. The Acela express train (search) can travel up to 150 mph but goes much slower through Connecticut.