A young girl was killed and her two sisters, along with a boy, were critically injured Thursday morning after their school bus and a dump truck collided, police said.

The accident happened just after 8 a.m. at Route 528 and Old York Road in Chesterfield Twp., Burlington Co., south of Trenton, officials said.

The bus, carrying 25 kindergarten through 6th grade students to Chesterfield Elementary School, ended up crumpled against a utility pole. The truck went off the road and into a grassy area, where it left deep tire marks.

The 11-year-old girl who died, Isabella Tezsla, was identified as a triplet daughter of a New Jersey state police Sgt. Anthony Tezsla. Her sisters, Sophie and Natalie, are being treated at Cooper University Hospital in Camden.

One other student on the bus, a boy, also was critically injured.

Another boy being taken from the scene by his mother said "this big truck just came and slammed right into us." His mother did not want his name used. The boy said the crash left some of his fellow students with bloody faces.

Students on the bus said they were wearing their seat belts.

Both the bus driver and the driver of the dump truck involved in the crash were hospitalized, but neither was seriously injured.

The school had counselors on hand to help students and staff cope with the tragedy on Thursday. All after-school activities were canceled. The school was previously scheduled to be closed Friday and Monday for a four-day weekend.

Gov. Chris Christie issued a statement saying his "thoughts and prayers are with everyone involved." He planned to comment further after more information was released on the accident.