(CNN) -- The Oregon State Penitentiary was on lockdown Sunday night after a series of fights broke out during the day, a prison spokeswoman said.
Some corrections officers and inmates suffered minor injuries in the fighting, spokeswoman Michelle Whitney Dobson said.
"We are continuing an investigation into the cause of the disturbance," Dobson said.
The trouble began just before 2:30 p.m. Sunday, when staff at the Salem, Oregon, prison responded to a fight among inmates at the institution's recreation building, the Oregon Department of Corrections said in a statement.
Staff personnel used chemical spray to break up the fight, and six inmates were taken to disciplinary segregation.
While staff members were responding to the fight, about 75 other inmates left the recreation building and began fighting on the recreation yard, the department said. Staff members fired one warning shot and used chemical spray to control the situation.
The inmates were segregated from the general population and the penitentiary was placed on lockdown, the department said.
All activities and visits were canceled for the rest of the day and for Monday, it said.
CNN's Greg Morrison contributed to this report.