GRANITE (AP) -- One inmate died and three others were injured in a brawl Sunday night at the Oklahoma State Reformatory, a corrections official said.

The fight broke out about 7 p.m. Sunday in the exercise yard while inmates were out for their evening recreation time, said Jerry Massie, spokesman for the state Corrections Department.

The prison was locked down after the fight was contained, Massie said.

The names of the injured and dead were being withheld until families were notified, Massie said. He said he did not have any information about the type of injuries suffered by the three inmates who were sent to nearby hospitals.

Massie said he does not know what triggered the fight. No staff reported injuries, he said.

About 900 men are housed at the medium-security Oklahoma State Reformatory, according to the Corrections Department Web site. The prison opened in 1910.

One other inmate has been killed in prison violence this year.

Adam Lippert, 32, was stabbed to death March 22 when 40 black inmates rushed him and 14 other white prisoners at the Cimarron Correctional Facility in Cushing.

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Information from: The Oklahoman, http://www.newsok.com