LINCOLN, Neb. — Five people died in two crashes in western Nebraska that began when mechanical problems forced a truck to stop on Interstate 80, investigators said Monday.

The first crash occurred early Sunday about 40 miles from the Wyoming border, where a tractor-trailer rig ran into the stalled truck on the interstate’s westbound lanes. A second semi then struck a car that had stopped because of the first accident, and the driver of that rig faces manslaughter charges.

The tractor-trailer driver who hit the stalled truck in the first accident died. The second fatal crash happened about 2 miles east of the first site, when authorities say rig driver Josef Slezak, 36, of Rivergrove, Ill., slammed into the back of a 2010 Ford Mustang.

The force of the crash pushed the Mustang into a 2007 Toyota Corolla, which in turn was shoved beneath the semi that was sitting ahead of it. The lone driver of the Mustang died, as did the Corolla driver and two juveniles who were passengers.

The crash in the Nebraska Panhandle kept the interstate closed for more than 14 hours Sunday.

Slezak is charged with four counts of manslaughter, a felony, and one count of careless driving, a misdemeanor, said Cheyenne County Attorney Paul Schaub.