SAN FRANCISCO (AP) — San Francisco officials say they have arrested three men in the death of a construction worker who was crushed by a steamroller being driven by an untrained employee.

District Attorney George Gascon announced Wednesday Michael Sommer, Manuel Silao and Ramiro Pena were arrested Tuesday in the 2016 death of a fellow employee. The victim was not identified.

He says a thorough investigation by Cal/OSHA, the state's workplace safety agency, found the men allowed a worker to operate the heavy roller at a city road project even though he had never operated one.

Gascon says the men and L C General Engineering and Construction, Inc. are being charged with one felony count of involuntary manslaughter and three felony violations of the labor code.

All will be arraigned by September 24.