"I am shocked and filled with sorrow following the events of last night," Jason Ravnsborg said.
The annual rally started on Friday, drawing thousands of maskless riders to the streets and bars of Sturgis.
Sources said an arrest has been made in the incident. There was no confirmation from police.
The Centers for Disease Control and Prevention issued more than 100 recommendations to the Smithfield Foods pork-processing plant on Thursday, as the facility works to reopen following a coronavirus outbreak.