Five more staff members were injured during a second altercation at Oak Park Heights prison on Sunday, the state Department of Corrections said Monday.

The fight Sunday involved one prisoner. All of the staff members were seen at the hospital and released.

The incident is under investigation, and prison spokeswoman Sarah Fitzgerald said she could not release any other information.

It was the second fight at the maximum security prison in the past three days. On Friday night, five staff members were injured in a fight with prisoners. They, too, were released from the hospital the same day.

Oak Park Heights opened in 1982 and houses up to 473 offenders, most of whom are classified as “maximum custody or extreme risks to the public,” according to information at the state’s website.

Pat Pheifer