NEW YORK - A subway train carrying 1,000 passengers shook through a tunnel, tilted and derailed on Friday, injuring more than a dozen people and frightening scores of others with sparks, smoke and sudden darkness.

Four people suffered serious injuries and were hospitalized, firefighters said. Some complained of chest pains. Fifteen others were treated at the scene.

The express F train was heading for Manhattan and Brooklyn when six of its eight cars derailed at 10:40 a.m. about 1,200 feet south of the 65th Street station in the Woodside section of Queens.

Passenger Rashmi Basdeo said the train suddenly "started to tilt and shake."

"It was scary," said the sales associate from Queens, who was taking the train to work in Manhattan. She said she held onto a post as the train came "screeching to a stop."

"We knew it was derailed from the sounds and the position of the car," she said.

Dozens of firefighters, police officers and paramedics converged. They used ladders to help passengers descend from the train to track level and guided them along the track to a sidewalk opening. The derailment happened about 30 feet below street level. Power was cut to the third rail to aid the rescue.

Deputy Assistant Fire Chief James Leonard said the middle six cars of the eight-car train derailed but remained upright.

The cause of the accident, which damaged the express tracks, was unclear.

There was no switch in the area, and the tracks were no more than 20 to 30 years old, Metropolitan Transportation Authority chairman Tom Prendergast said. The train's operator and conductor will be tested for drugs and alcohol, he said.

Passenger Tayyib Siddiqi said the accident started "with a little bit of turbulence."