At least five people are dead following a charter bus crash into a freeway sign in Merced County. The Associated Press reports the collision occurred in the early morning, and that the bus was split nearly in half by the force of the impact.

In route to Sacramento from Southern California, the bus was on Highway 99 north of Atwater when it veered into the sign at approximately 3:35 a.m.

"The pole went through the center of the bus, and that's where the injuries were sustained," California Highway Patrol Officer Moi Onsurez told the AP.

The bus carried 30 passengers, and the driver was among the injured. First responders used ladders to pull people to safety through shattered windows, and five passengers are reported to have been hospitalized.

The cause of the crash remains unknown, and NBC reports that northbound 99 is closed as officials investigate.

Related: LA-To-SF Greyhound Bus Flips On 101 In San Jose, Killing Two