A sheriff says negotiations are continuing with about 2,000 inmates who have seized control of part of a federal prison in South Texas in what he called an "uprising."

Willacy County Sheriff Larry Spence didn't go into detail about the negotiations Saturday but said there are no hostages involved and only minor injuries reported.

Management & Training Corp., the private contractor that operates the Willacy County Correctional Center for the U.S. Bureau of Prisons, said inmates became disruptive early Friday. They're upset with medical services and refused to perform work duties.

The contractor says inmates "breached" their housing units and reached the recreation yard. The Valley Morning Star reports fires were set inside three of the prison's 10 housing units.

MTC says the facility primarily holds immigrants with criminal records.