Massachusetts State Police said 28 of the people who were injured when a bus struck an overpass in Boston have been released from the hospital, while seven remain hospitalized.
Police said the driver -- Samuel Jackson -- failed to heed low-clearance warning signs.
Of the seven still hospitalized, one is in critical condition, four are in stable condition, one is in serious condition and one is awaiting discharge.
The Calvary Coach bus was carrying 42 people and was heading back to the Philadelphia area when it struck an overpass on Soldier's Field Road in Boston, a major crosstown road, at around 7:30 p.m. Saturday, Massachusetts State Police said. Some passengers were trapped for more than an hour as rescue crews worked to free them.
Authorities said the bus did not belong on the road, where a 10-foot height limit is in place and oversized vehicles are not authorized.
State police said Jackson "failed to heed signs" warning of the height limit and will likely be cited for an over-height violation.
The investigation will determine if he faces more serious charges, state police said. The driver was not injured.
Jackson looked down at his GPS and saw the bridge when he looked up but it was too late to avoid hitting it, Ray Talmedge, owner of the Philadelphia-based Calvary Coach Bus company said.
The students were part of a Destined for a Dream Foundation group, Talmedge said. Officials with the Bristol, Pa.-based group, a nonprofit that helps underprivileged youth, refused to comment on the crash when reached by phone.
The group's Facebook page said the trip to Harvard was to "visit the campus, sit with the office of cultural advancement, followed by a tour of the campus ... followed by Harvard Square (shopping, eating, site seeing...etc...) This should be a fun time for all!"
None of those injured was identified, and state police said they did not know how many of the injured were adults and how many were juveniles.
The bus suffered significant damage in the crash. The front part of the roof was pushed in while the center section bowed downward. Photos posted on the Fire Department's website showed firefighters standing on the top of the bus using boards to extract people. The last victim was freed from the bus around 9 p.m., according to the department.
The Massachusetts Bay Transportation Authority sent buses to pick up other passengers and get them out of the frigid temperatures.
Soldiers Field Road curves along the Charles River and passes by Harvard and Boston University. It is a major roadway to the Massachusetts Turnpike. The road was reopened Sunday after crews removed the bus and repaired guardrails.
The circumstances of the crash recalled a similar accident in Syracuse, N.Y., in 2010. The driver of a double-decker Megabus missed his exit and was using a personal GPS to find the bus station. He passed 13 low-bridge warning signs, some with flashing yellow lights, before hitting an overpass. Four people were killed. The driver was acquitted of homicide charges.
In December, a driver who prosecutors said was nearly asleep at the wheel was acquitted of the most serious charges in a crash that killed 15 gamblers returning to New York City from a Connecticut casino in 2011.
Federal officials stepped up enforcement of bus safety regulations last year, closing more than two dozen operations that mostly ferry passengers in the busy East Coast transportation corridor. It was the largest single federal crackdown on the industry.
Buses carry more than 700 million passengers a year in the United States, according to the American Bus Association.