SACRAMENTO (CBS13) — A tow truck crashed into the Sacramento River from the Pioneer Memorial Bridge Tuesday evening, according to Sacramento Fire Captain Keith Wade.

Capt. Wade said the truck was on the westbound side of Highway 50 at the highest point of the bridge when it went off the south side of the bridge into the Sacramento River.

Crews have not located any victims nor the vehicle. Wade said recovery crews may have to call off the search until the daylight.

It is still unclear what caused the truck to go off the highway.

Officials said other vehicles were involved in the incident on the highway that ended up with flat tires.

It is unclear if there are any victims.

This is a developing story.