NUTLEY, N.J. (AP) — Authorities are trying to determine what caused a fire truck to overturn in New Jersey, injuring three firefighters.

Essex County prosecutors say the truck wound up on its side late Saturday night, not far from the Nutley fire department's headquarters.

But they have not said how the accident happened or if the truck was responding to or returning from a call at the time.

Two of the injured firefighters were treated at a hospital and later released. But the third remained hospitalized Sunday.

The firefighters' names and details on the injuries they suffered have not been disclosed.