The crash happened around 10:20 a.m. on Interstate 80 in Mount Olive, located about 50 miles west of New York City.
Mount Olive Mayor Rob Greenbaum, who saw the aftermath of the highway crash from an overpass, described the scene as "horrific". Governor Phil Murphy said the two killed were a child and an adult. A student and teacher were killed, and 43 others injured.
The impact appeared to rip the bus from its chassis, and with its front end crumpled, it lay for hours in the median of I-80.
The bus is marked as a Paramus School District vehicle, and it is understood that a fifth-grade class trip from the district was scheduled for Waterloo Village, an historic site five miles from the crash scene.
The front end of the dump truck involved in the crash was mangled, and the condition of the truck driver wasn't known. Emblazoned on the back of the truck: "In God we trust".
Fifth-grade student Theo Ancevski, who was sitting in the fourth row of the bus and was treated at a hospital for cuts and scrapes, said he heard a scraping sound and the bus "toppled over". "I saw a few taken away on gurneys", he said.
Officials said the bus driver is a district employee, and the school bus is owned by the Paramus Public Schools.
The dump truck was also damaged in the crash.
The Morris County prosecutor's office confirms "there are fatalities as a result of this crash" but hasn't said how many. A spokeswoman for Atlantic Health confirmed that patients were taken to the company's Morristown and Hackettstown centers, but would not elaborate.
At least two of the victims have been sent to St. Joseph's Medical Center in Paterson. She declined to provide further details. Additional information regarding the bus accident can be obtained by calling 888-407-9628.
Evening activities have been cancelled, but aftercare will continue.
Qureshi said students on the other buses didn't find out about the crash until they arrived back at school. "Our hearts go out to the families of our students, staff and community members". "But luckily, first responders, everybody there helped get all the kids out safely from what we could see". Officials say school will be in session on Friday with grief counselors available.
The quick emergency response saved lives, Tedesco said.