The crash occurred about 10:20 a.m. in Mount Olive Township in northern New Jersey's Morris County, Governor Phil Murphy told a news conference. The bus was carrying 38 students and seven adults, including the driver.
"Some patients are in critical condition and currently undergoing surgery, so please keep everybody in your prayers," Murphy said.
“There is an awful lot we just don’t know,” the governor said, adding details of the crash were not being released pending an investigation.
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. The dump truck seemed to be mostly intact.
The bus was carrying students from East Brook Middle School in Paramus to Waterloo Village, a restored 19th century canal town, officials said.
“The bus flew off of the wheels, but it hit the metal thing on the side of the highway,” fifth-grader Theo Ancevski said. He told reporters he escaped through an emergency door on the bus.
"A lot of people (inside the bus) were screaming and they were like, hanging from their seat belts," he added. U.S. fifth-graders are generally aged 10 or 11.
The crash temporarily shut all westbound lanes of I-80, State Police said.
Two other buses in the field trip convoy also carrying fifth-graders on the same trip returned to Paramus, officials said.