BOSTON (WHDH) -- Dozens of emergency vehicles were on scene Saturday night after a tour bus transporting high school students failed to clear an overpass on Soldiers Field Road.

Fire fighters and EMTs climbed on top of the bus to cut people free in a complicated rescue.

“We had special saws and equipment to free the trapped victims. What we had to do was get the four people- cut the roof off the top of the bus to get four victims that were seriously trapped in the back of the bus,” said a fire official.

At least three people are critically injured. Thirty-two people in total were taken to hospitals.

Many of the victims stayed warm in MBTA buses until they could be transported to hospitals. Many of them and many of the witnesses that watched the aftermath unfold are stunned by what they saw.

“I couldn’t believe it. I thought the bridge blew up or something because they’re doing construction on the bridge all the time…so I just automatically assumed something, you know, the bridge fell,” said a witness.

“It’s horrible. It’s horrific. On such a cold night too you wonder if everyone’s okay, you wonder who the driver is, it’s what you don’t know,” said a witness.

Investigators will be on scene for most of the night. They believe the driver never saw signs showing the tunnel clearance was just 10 feet high.