Video:  School bus accident on Maryland highway on July 5, 2006

The Associated Press

ABERDEEN, Md. — A bus carrying children on a field trip crashed Wednesday on Interstate 95 in northeastern Maryland, sending more than 50 people to hospitals, officials said.

Four were seriously injured and flown to Johns Hopkins Children's Center in Baltimore, said Rich Gardiner, a spokesman for Harford County Volunteer Fire and EMS. Fifty-three people with minor injuries were taken to other hospitals.

The cab part of a tractor-trailer also was involved in the crash, said Sgt. David Jones of the Maryland State Police. Further details were not immediately available. Sixty people were aboard the bus.

Two of the seriously injured children were in serious condition, and two were in good condition, said David Hare, a hospital spokesman.

The bus was returning to Norris Square Day Camp in Philadelphia from the National Aquarium in Baltimore, Jones said.

Phones at the day camp rang unanswered Wednesday. Other camp officials did not immediately return messages.