TECUMSEH, Neb. (AP) — Two more staff members have been attacked by prisoners at a state prison in southeast Nebraska.

The Nebraska Correctional Services Department says the two were assaulted early Sunday morning at the Tecumseh prison. One of them suffered what the department described as serious but non-life-threatening injuries. The department didn’t provide details on how the attack occurred or say how many prisoners took part. It did say no weapons were involved.

The staffers’ names haven’t been released.

In recent years the department has reported several incidents of violence at the prison, which sits 62 miles (100 kilometers) south of Omaha. Authorities say two inmates were killed by other prisoners in a March uprising, and two more died during rioting in May 2015.