A trolley rear-ended another trolley that was stopped between two underground stations in downtown Boston on Friday night, injuring about 50 people, and one of the conductors told police he was texting at the time of the crash, officials said.

About 100 people were evacuated, and 49 were taken to area hospitals, but officials said their injuries did not appear to be life-threatening.

The 24-year-old operator of the moving trolley, who was the most seriously injured, admitted to police that he was sending text messages from his cell phone when the accident occurred, Massachusetts Bay Transportation Authority general manager Dan Grabauskas said.

The MBTA has stepped up enforcement of the rule against cell phone use by operators following a trolley crash in Newton last May that killed the driver of a trolley that collided with another. Although there were reports the driver was using a cell phone just before the crash, an investigation ultimately determined there was no evidence she was using her phone.

Grabauskas said the operator of the trolley that struck the parked trolley admitted to investigators who interviewed him in a hospital he saw the red light ahead of him as he was texting, but it was too late to stop.

"I can tell you it's difficult to contain my outrage at hearing this," Grabauskas said.

Officials would not release the conductor's name, but MBTA spokesman Joe Pesaturo said he had been on the job for less than two years.

Most of the victims suffered cuts or skeletal injuries, said John Gill, deputy superintendent of Boston EMS. Two people had chest pains.

Some passengers had to be extracted from the trains, deputy fire chief Richard DiBenedetto said. Others were taken from the station on stretchers or backboards.

The collision occurred at 7:18 p.m. between Park and Government Center stations. A westbound two-car trolley was stopped at a red signal, waiting to enter Park Station, when it was hit by another two-car trolley.

The damage was limited to the front of the moving train and the rear of the train that was struck, Grabauskas said.

An investigation will try to determine why the moving trolley did not stop. Grabauskas had no estimates on how fast it was traveling.

Green Line service between the stations was shut down after the crash.

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