Students screamed and some were left "hanging from their seat belts", he said. Students on two other buses on the field trip returned to the school about 50 miles (80 kilometers) from the crash site and were reunited with their parents.
Several people were admitted to multiple New Jersey hospitals with injuries, officials said. The buses returned to the school after the crash. It is unclear how many students were aboard the bus or the number of vehicles involved in the collision.
Theo Ancevski, a student riding on the bus, told the AP he was sitting in the fourth row from the front when it crashed. The body of the bus was nearly completely torn off the vehicle's frame. He says he "heard a scraping sound" and the bus "toppled over".
The Paramus (puh-RAM'-uhs) school district says the bus was taking students to Waterloo Village, a historic site. Forty-three people from the bus and the truck driver were taken to three area hospitals, where some were listed in critical condition.
A statement from Morris County Prosecutor Frederic Knapp said that the exact number and the identity of the victims was is being withheld pending formal notification of next of kin.
All lanes of Interstate 80 have been shut down.
At the scene, the school bus appeared to be separated from its undercarriage, northjersey.com reported.
'Crash investigation on Route 80 by mile marker 25.
The front end of the red dump truck was mangled in the wreck, which took place about 50 miles (80 kilometers) west of NY.
"It's a horrific scene", he said.
A sign outside of the East Brook Middle School in Paramus informed people to go to the auditorium for updates on the accident. He calls the crash a "tragedy".
Hackettstown Medical Center told News 12 New Jersey they are receiving 10 patients from the crash. All field trips have been canceled for the rest of the school year.
Mount Olive police said it was responding to the incident but would not give further details. The front of it was barely recognizable, a mangled chunk of broken-apart machinery spread from the highway shoulder lane through the guardrail and into the grassy median, where police and first responders are seen tending to stunned children.
A school bus that collided with a dump truck in New Jersey had markings for a school district that had a scheduled class trip to a nearby historic site.
East Brook Middle School is home to fifth to eighth grade pupils.
Mayor of Mount Olive Rob Greenbaum said: "There's an incredible emergency response from throughout Morris County and by State Police".
The front end of the bus was severed from the vehicle and the body of the bus was separated from its chassis, which remained on the highway.
About 10 victims have been taken to St. Clare's Dover Hospital and St. Clare's Denville Hospital, based on Communications Director Patty Montgomery. The extent of their injuries wasn't known.