Firefighters and EMTs are on Soldiers Field Road near the Genzyme plant trying to get people out of a bus that was too tall for the Western Avenue underpass it tried to traverse inbound around 7:30 p.m. State Police said the bus was "overheight."

The road is shut in both directions as firefighters and EMTs set up a triage area and order more backboards. Boston EMS says 32 passengers were injured; three of them critically. One of those had head trauma and required help breathing.

An hour later, two passengers were still trapped in the rear of the bus; not long after, firefighters got one of them out. The final passenger was extricated shortly before 9 p.m.

The Boston Fire Department reports the bus had just left Harvard on its way to Pennsylvania with 42 people on board, from a non-profit group's day trip to Harvard and Harvard Square. Federal records show Calvary Coach is a small charter company based in Philadelphia - with just two buses.

State Police say the road will remain shut for much of the night both for an investigation into the accident and for removing the bus.

More photos by Scott Eisen.