(CNN) The leader of an armed militia that held hundreds of migrants at the US-Mexico border was attacked at a New Mexico detention facility, authorities said Wednesday.

Larry Mitchell Hopkins, the 69-year-old leader of the United Constitutional Patriots, was treated for non-life-threatening injuries after the alleged battery this week at the Doña Ana County Detention Center in Las Cruces, according to a press release from the county.

"He was attacked by other detainees," said Kelly Jameson, a spokeswoman with Doña Ana County. "We are still conducting an investigation, but it could be possible that three other detainees were involved."

She didn't have further details on the alleged battery.

The FBI arrested Hopkins last week. He was charged Monday with being a felon in possession of firearms and ammunition in a case that stems from a November 2017 search of his Flora Vista home, according to a criminal complaint.

Read More