Updated at 6:40 p.m. ET: CHESTERFIELD, N.J. - A school bus carrying elementary school children collided Thursday with a dump truck, killing an 11-year-old daughter of a state trooper and critically injuring three other students — two of them the triplet sisters of the dead girl, authorities said.

 The accident occurred shortly after 8 a.m. at a four-way intersection in the town of Chesterfield, south of Trenton. It sent the bus, which was carrying 25 students, crashing sideways into a traffic signal pole, crumpling the side. Police said 17 students received injuries, most of them minor.

State police identified the father of the triplets as Sgt. Anthony Tezsla, The Associated Press reported. 

His daughter Isabella was killed. Her sisters, Sophie and Natalie, were listed in critical condition at Camden's Cooper University Hospital, along with Jonathan Zdybel, also 11.

A parent who came to pick up her bruised children said there were a number of injuries and that many of the injured students were hospitalized.

At least three medical helicopters were called to the scene, reported NBCPhiladelphia.com.

A boy picked up 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 seatbelts. But a mother of one of the children told television station NBC10 in Philadelphia that some children were still tossed into the aisle.

Get the latest on the school bus crash from NBCPhiladelphia.com 

John Kelly, whose 11-year-old daughter attends Chesterfield Elementary School, said the trooper's triplets were in his house just a short while ago and played sports with his daughter.

"It's devastating. My wife can't come out or anything," said Kelly, who was picking up his daughter, who walks to school, Thursday afternoon.

The bus ended up upright against a large traffic signal pole at the intersection. The bus was crumpled where it hit the pole.

A large dump truck ran off the road and into a grassy area, where it left deep tire marks.

The cause of the crash wasn't immediately known, reported NBCPhiladelphia.com. Surrounding roads were closed as authorities investigated. 

The Associated Press and NBCPhiladelphia.com contributed to this report.