Fighting among inmates at the Oregon State Penitentiary dining hall has led to a lockdown.
A Corrections Department statement says about 30 people were involved, and nobody was hurt so badly as to require treatment outside the prison.
The fighting broke out shortly after noon Thursday.
No information on what caused it was immediately available.
Visitation was canceled.
The penitentiary is Oregon's oldest prison and the only maximum security prison among 14 institutions. It houses about 2,000 people.
Oregon prison officials have reported several instances of inmate fighting in 2014.
At Two Rivers near Umatilla, 24 inmates were involved in a fight in mid-April.
At Eastern Oregon, a warning shot stopped a small fight in April. In May a series of fights led to a lockdown lasting several days.