Seven people are dead and 37 were injured after a passenger bus crashed in Mississippi early Saturday morning.

The passenger bus was traveling westbound when it left the roadway and overturned on Interstate 20 in Warren County, according to the Mississippi Highway Patrol, which responded to the scene around 12:40 a.m.

No other vehicles were involved in the crash, the agency said in a news release. It’s not clear what caused the crash at this time.

Six passengers were pronounced dead on the scene and one died in a nearby hospital, according to the Mississippi Highway Patrol. The identities of the victims have not been released pending notification of next of kin.

Thirty-seven passengers were taken to hospitals “with unknown injuries.” It’s unclear how many passengers were on the bus in total.

“This crash remains under investigation by the Mississippi Highway Patrol and the Commercial Transportation Enforcement Division,” the Mississippi Highway Patrol said.

This is a developing story. Please check back for updates.