A SCHOOL bus taking children on a field trip to a New Jersey historic site has collided with a truck, ripping the bus apart and killing a teacher and student.

The crash left the bus lying on its side on the guardrail of Interstate 80 in Mount Olive, its undercarriage and front end sheared off and its steering wheel exposed.

Some of the victims crawled out of the emergency exit in the back and an escape hatch on the roof. More than 40 people were taken to area hospitals.

"I heard a scraping sound and we toppled over the highway," said student Theo Ancevski, who was sitting in the fourth row of the bus and was treated at a hospital for cuts and scrapes. "A lot of people were screaming and hanging from their seatbelts."

New Jersey Governor Phil Murphy said that one adult and one student were killed. Murphy said the driver of the truck was alive at the hospital, but officials didn't reveal his condition.

The front end of the red dump truck was mangled in the wreck, which took place about 80km west of New York.

Police didn't release details of how the crash happened, but the trucking company had a string of crashes in recent years and a higher than average rate of violations that sidelined its vehicles, according to federal safety data.

There were 45 people, including 38 students, on the bus. Forty-three people from the bus and the truck driver were taken to three area hospitals, where some were listed in critical condition.

The bus was taking students from East Brook Middle School to Waterloo Village, a historic site depicting a Lenape Indian community and once-thriving port about 8km from the crash scene.

Some of the children were still inside the bus and some were outside when first responders arrived, according to Jeff Paul, director of the Morris County Office of Emergency Management.

"We had patients laying all over the median and on the interstate," Paul said. "There were all kinds of injuries, every injury type you could expect in a crash of his magnitude."

Paul said some of the first responders were "very emotionally upset. It was a rough scene to see."

According to the National Highway Traffic Safety Administration, 118 people on school buses were killed in crashes from 2007-2016, the last year for which data is available.

Of those killed, 68 were passengers - including 58 school-age children - and 50 were drivers. School bus crashes killed 902 people in other vehicles over that span.