A crash on Interstate 280 involving a dump truck left at least seven people injured, including three New Jersey state troopers.

New Jersey State Police say that the troopers were on the eastbound side of the highway in West Orange around 10 a.m. Tuesday investigating previous, unrelated car crash when the dump truck collided with the troopers and their vehicles.

Officials say that two of the troopers sustained serious, but injuries that were not considered life-threatening. Another trooper sustained minor injuries. Details of those injuries were not immediately released. At least four other people sustained minor injuries.

Acting Gov. Sheila Oliver says she has visited the troopers in the hospital.

“While this is an ongoing investigation, it should remind us all of the dangers our first responders can encounter on our roadways. We wish all of those injured a speedy recovery,” Oliver wrote on Twitter.

The eastbound side of I-280 was closed for about nine hours between exits 8 and 11. Those lanes have since reopened.

After the crash, the dump truck was seen lying partially on its side against the guardrail of the highway. The front of the dump truck was pushed up against the back of an ambulance, which was already at the scene for the previous crash.

It was not immediately clear why the driver of the dump truck was unable to avoid hitting the other cars.