SAN FRANCISCO (AP) — San Francisco prosecutors have charged the president of a construction company and two employees with involuntary manslaughter in the death of a worker who was run over by a steamroller.

The district attorney's office announced the charges on Wednesday against LC General Engineering and Construction, Inc. President Michael Sommer, project manager Manuel Silao and foreman Ramiro Pena.

Prosecutors say the men allowed a worker to operate the steamroller even though he had not received proper training and had never previously operated the machine. The worker lost control of the steamroller in January 2016, and it crushed a co-worker.

Prosecutors say Pena pleaded not guilty on Wednesday. Sommer and Silao have not yet been arraigned. It was not clear whether they had attorneys.

Phone messages at the company were not immediately returned.