DORCHESTER (CBS) – Seventeen people were injured when two MBTA trolleys collided on the Mattapan-Ashmont line in Dorchester Friday afternoon.

At about 3:15 p.m., the two trolleys collided on the inbound track between Cedar Grove and Butler, according to the MBTA.

A rider told WBZ-TV’s Juli McDonald the trolley he was in came to a stop on the tracks before it was struck from behind.

“We stopped because we couldn’t move, because there was a trolley ahead of us at Ashmont,” Antonio Rodriguez said. “One came from behind us I guess and just crashed against us. So hard. Everyone just was freaking out.”

Rodriguez says a man had a bad head injury and “was bleeding all over the place.”

The location between stops somewhat complicated the response. Boston EMS says a total of 17 patients were evaluated and 16 were transported to area hospitals.

“There was one patient that was moved on a sled device that actually allows us to glide them over snow,” said Boston EMS Deputy Superintendent Steven McHugh.

Boston Fire examining area around the other trolly involved. @MBTATransitPD on scene investigating. pic.twitter.com/fCApz5QJ9P — Boston Fire Dept. (@BostonFire) December 29, 2017

All of the injuries were non-life threatening. “The hardest thing today was keeping the patients out of the cold,” McHugh said.

Several passengers were seen leaving the trolleys and walking on the snow-covered tracks. Other passengers were escorted by firefighters through Cedar Grove Cemetery.

Investigators are probing the cause of the crash. “A thorough investigation into the incident will include inspections of the equipment and interviews with the trolley operators,” the MBTA said.

Investigators say neither drugs nor alcohol appear to be factors. They are looking into whether a stopped trolley on the opposite side of the tracks had anything to do with the two inbound cars colliding.

Shuttle buses replaced service in both directions on the Mattapan Line.