Authorities are investigating a deadly chain-reaction crash on Highway 99 south of Fresno that left one person dead and multiple others injured Sunday morning.

The California Highway Patrol said at least 15 vehicles were involved in the crash, including a semi-truck, around 9:15 a.m. between North and Cedar avenues. Investigators reported that two separate collisions occurred after traffic slowed, and some motorists were unable to stop in time.

The Fresno County Coroner’s Office identified the victim as 61-year-old Gustavo Villanueva Vargas. CHP said Vargas and another person exited a vehicle and were struck during the second collision.

Several individuals were taken to local hospitals. Officials believe fog contributed to the crash. The cause remains under investigation.