A tour bus carrying more than two dozen Philadelphia eighth-graders flipped over on I-95 Monday morning after a car crashed into it roughly two hours outside Washington, D.C.

A student and teacher were rushed to area trauma centers.

The car clipped the front of the charter bus just before 9:30 a.m. near the Havre de Grace exit, according to Philadelphia school officials. The group from C.W. Henry School was on a field trip to see the Lincoln Memorial, the Martin Luther King Memorial and the Newseum.

Maryland State Police spokesman Greg Shipley said the multicar crash started when a driver tried to pass the bus.

"For reasons unknown at this time, the driver lost control of the vehicle, ran off the left side of the interstate, then back across all lanes of the interstate, hitting the front of the bus as it traveled across the roadway," said Shipley.

The bus struck an embankment and a tree before overturning, he said.

All 30 bus passengers were taken to area hospitals for medical evaluation, including 26 students, two teachers, the driver and a chaperon.

Three crash victims are being treated at Delaware hospitals, officials said.

One student was flown to Nemours Alfred I. duPont Hospital for Children, said spokeswoman Nancy D'Argenio. She did not provide the child's age, injuries or condition.

Two people were taken to Christiana Hospital near Stanton. One is in serious condition and the other in good condition, spokeswoman Kathy Hinde said. Hinde could not provide the patients gender, age or provide details of their injuries.

Philadelphia Schools Superintendent William Hite said some of the bus passengers were released from the hospital by Monday afternoon.

District officials are asking parents to call 215-400-5858 for more information.

Two reunification sites have been set up. One is at the Havre de Grace Ambulance Corps. The other is at C.W. Henry School in the Mt. Airy section of Philadelphia.

"This was a devastating event for all involved. Student safety, on and off school grounds, is of paramount importance, and the city will continue to do whatever we can to support the school district and assist families impacted by this tragedy. I pray for the full and speedy recovery of those who were hurt," said Philadelphia Mayor Jim Kenney in a statement.

Shipley, with Maryland State Police, said the driver of the car that hit the charter bus was taken in for questioning, but has not been arrested.

The investigation into the crash is ongoing.

WHYY reporter Cris Barrish contributed to this report.