BOSTON, DEC. 28 -- A trolley car was struck from behind by another trolley about 6:45 a.m. today as it let off commuters in the underground Arlington Station, injuring 33 people, at least one critically, officials said.

The driver of the moving trolley, who told officials his brakes failed, tested positive for alcohol in his blood, said Peter Dimond, a transit spokesman. The identities of the two drivers were not released, but the one who tested positive for alcohol was suspended, Dimond said.

Most of the injured were treated and released at hospitals. One person was reported in intensive care at New England Medical Center, and another was admitted to University Hospital. The accident involved two inbound Green Line trains on the same track.

"I just screamed out, 'Everybody hang on and get down! We're going to hit!' " said Steve DePaula, a passenger on the moving trolley. "It just seemed like seconds later we smashed into the trolley in front of us. People just went flying everywhere."

DePaula said the moving trolley was going faster than usual. Thomas Glynn, general manager of the Massachusetts Bay Transportation Authority, said transit officials did not know the second car's speed.

"I was looking at the lady across from me," said Ernest Jones, a passenger on the stationary trolley. "Next thing I knew, the lights went out, and she was on the floor. I saw one man in the back on the floor on his back, crying, obviously in agony, hurt."

Glynn said the driver of the moving trolley, 64, had been with the transit authority for 20 years. The other driver, 54, had worked for the authority for 22 years, he said.

Mayor Raymond Flynn, on the scene soon after the accident, said initially he was not ready to believe reports of another rail crash so soon after the recent Amtrak accident at Back Bay Station, which remains under investigation.

More than 250 people were injured there when an Amtrak train struck a commuter train.