The San Francisco Fire Department responded to multiple car crashes, caused in a chain-like reaction, Thursday around 2 p.m. on the Interstate 80 tunnel across Treasure Island — leaving at least 18 people hurt, all of whom suffered non-life-threatening injuries.

At least four ambulances rushed onto the Bay Bridge Thursday afternoon to offer aid to over a dozen people injured in a multi-car crash. Two of the eighteen people cited injured required transportation to a nearby ER center; the other sixteen — eight adults and eight pediatric patients — were treated on-site, having suffered mild to moderate injuries that didn’t require hospitalization.

According to the department, the crash was later described as a "multi-casualty" after first being noted as a "multi-injury" event; it's unclear how many casualties might have been caused by the crash.

Per the Chronicle, the multi-vehicle crash began when a car collided with a wall at about 12:40 p.m.; this then caused as many as five other cars to crash inside the tunnel, according to initial reports; heavy traffic delays were reported, which were cleared a little after 2 p.m. after emergency crews cleared all eastbound lanes.

The incident is now being investigated by the California Highway Patrol.

Related: Getty Images/DianeBentleyRaymond