By CBSBoston.com Staff

BOSTON (CBS) – More than 20 people were treated for injuries after two Green Line trains crashed on Commonwealth Ave. in Boston Friday. The collision happened shortly after 6 p.m. on the B Branch near Boston University’s Agganis Arena.

MBTA General Manager Steve Poftak said the two trains were traveling westbound when the trailing train struck the one in front of it.

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Brian Sirmon was on the now badly damaged train that was stopped when it was hit from behind. “All of a sudden it jerked forward really quickly,” Sirmon said. “People were thrown on the floor.”

The MBTA said 25 people received medical attention after the crash. EMS workers from Boston and Brookline transported 23 people to hospitals.

Two Green Line trains collided near Boston University (WBZ-TV)

“There was a girl who was thrown on the floor and I think she dislocated her shoulder,” Sirmon said. “She was pretty bad. That was the reason I think that people started calling 911.”

“Right now we are in the midst of conducting an investigation,” Poftak said. “We will obviously get to the bottom of this. This should not happen and we will find out why it happened and we will ensure that it won’t happen again.”

Poftak said the driver of the rear train was among those transported to the hospital.

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“Obviously at some point they became too close together, that is a situation that should not happen,” Poftak said. “The investigation will dig into why that happened.”

Poftak said the trains became de-railed after the crash. Once the investigation is complete, the trains will be re-railed and repairs will be made to any infrastructure that was damaged.

“It was definitely scary,” witness JC told WBZ. “I heard a big boom, and that’s what made my heart drop.”

JC, who was nearby when the crash happened, said passengers appeared to have neck and head injuries.

“So there was a woman that was coming off the train, and she had a lot of blood coming down her face,” JC said. “I had napkins, so I gave her some napkins and stuff like that.”

The MBTA said shuttle buses are replacing B Branch trains between Kenmore and Washington Street.

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State and federal investigators have been informed of the incident. It is unclear when service will be restored.

CBSBoston.com Staff