Four workers at Stillwater state prison were injured in an altercation Wednesday that led to a cell block lockdown, a prison spokesman said early Thursday. Two of the injuries were minor, while two required hospital treatment.

John Schadl, spokesman for the Minnesota Department of Corrections, said he could not provide many details about the midday incident at the men's prison except to say that two employees suffered minor injuries that did not require a trip to a hospital, while one contract employee and one correctional officer were hurt seriously enough that they were taken to a local hospital for treatment, then released.

He declined to say what role that inmates might have played in the altercation. "We have an active investigation underway, and we need to talk tomorrow [Thursday] about what we've learned and what we can say about it," Schadl said.