Investigators probe cause of school bus crash that killed 2

Emergency personnel work at the scene of a school bus and dump truck collision, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thurs

Emergency personnel work at the scene of a school bus and dump truck collision, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thurs

Emergency personnel work at the scene of a school bus and dump truck collision, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thurs

Emergency personnel work at the scene of a school bus and dump truck collision, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thurs

Emergency personnel work at the scene of a school bus and dump truck collision, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thurs

Emergency personnel work at the scene of a school bus and dump truck collision, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thurs

Emergency personnel examine a school bus after it collided with a dump truck, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thursda

Emergency personnel examine a school bus after it collided with a dump truck, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thursda

This photo shows an overturned school bus after it collided with a dump truck, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thursd

This photo shows an overturned school bus after it collided with a dump truck, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thursd

Emergency personnel work at the scene of a school bus and dump truck collision, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thurs

Emergency personnel work at the scene of a school bus and dump truck collision, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thurs

A dump truck sits on the road after it collided with a school bus, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thursday, May 17,

A dump truck sits on the road after it collided with a school bus, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thursday, May 17,

Emergency personnel work at the scene of a school bus and dump truck collision, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thurs

Emergency personnel work at the scene of a school bus and dump truck collision, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thurs

Emergency personnel examine a school bus after it collided with a dump truck, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thursda

Emergency personnel examine a school bus after it collided with a dump truck, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thursda

Emergency personnel examine a school bus after it collided with a dump truck, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thursda

Emergency personnel examine a school bus after it collided with a dump truck, injuring multiple people, on Interstate 80 in Mount Olive, N.J., Thursda

Emergency personnel respond to a crash after a school bus and dump truck collided in Mount Olive, N.J., Thursday, May 17, 2018. (Jay Faltings via AP)

Emergency personnel respond to a crash after a school bus and dump truck collided in Mount Olive, N.J., Thursday, May 17, 2018. (Jay Faltings via AP)

This image taken from WABC-TV video shows an overturned school bus after it collided with a dump truck, injuring multiple people, on Interstate 80 in

This image taken from WABC-TV video shows an overturned school bus after it collided with a dump truck, injuring multiple people, on Interstate 80 in

A dump truck sits near the scene after a collision with a school bus in Mount Olive, N.J., Thursday, May 17, 2018. (Jay Faltings via AP)

A dump truck sits near the scene after a collision with a school bus in Mount Olive, N.J., Thursday, May 17, 2018. (Jay Faltings via AP)

MOUNT OLIVE, N.J. (AP) — Investigators are working to determine why a school bus taking a group of fifth-graders on a field trip collided with a dump truck and tipped over on a busy New Jersey highway, killing a student and a teacher.

The crash happened Thursday morning on Interstate 80 in Mount Olive, about 50 miles (80 kilometers) west of New York.

Police declined to release details about how the crash happened, but it occurred on a stretch of highway just past the exit for Waterloo Village, where the group from East Brook Middle School was headed.

The bus wound up on a guardrail close to a spot for emergency vehicles to make a U-Turn onto the highway. A sign there reads "No Turns."

The impact of the accident tore apart the bus.