SAN FRANCISCO (CBS SF) — A San Francisco Muni bus operator was recovering Friday from injuries suffered when three passengers who refused to put on masks attacked the driver with a bat before fleeing, authorities said.

The incident took place after three young men boarded the bus at 11th and Division St. near the Potrero Hill neighborhood. They were not wearing masks as required by San Francisco’s COVID-19 health order.

READ MORE: South Bay Retailer Shutters Store in Response to Smash-and-Grab Crime Wave

Several times, the driver told the three they needed to put on face coverings if they wanted to remain on the bus.

READ MORE: Grieving Family Members Call for Justice for Slain Security Guard Kevin Nishita

Investigators said when the driver told them to get off the bus, one of the young men pulled out a bat and began battering the driver. The three then fled the scene.

The driver suffered non-life-threatening injuries and was expected to recover.

MORE NEWS: Warriors End Suns’ Win Streak at 18 With 118-96 Victory

Police have not provided a description of the three suspects or if their images were captured on security cameras.