McALESTER, Okla. (AP) _ An Oklahoma State Penitentiary inmate heading for a shower Friday pulled a homemade knife, seized the guard escorting him and held him hostage in his cell, prison officials said.

The inmate, Steven Allen Wainscott, 28, blocked the inside and outside windows of his cell to prevent security personnel from monitoring his movements, said prison spokeswoman Linda Morgan.

No injuries have been reported.

Negotiations continued with Wainright late Friday night, Ms. Morgan said. No demands had been made, she said.

Wainscott is serving a 20-year sentence for shooting with intent to kill. He has been incarcerated since July 1979, Ms. Morgan said.

Wainscott was leaving his cell to shower at 7:50 p.m. when he pulled a homemade knife from his undershorts and placed it at the throat of correctional officer Doug Turner, then pulled the officer back into his cell, Ms. Morgan said.

The inmate is in the administrative segregation unit of the maximum- security prison, which houses 40 inmates. The unit is on 23-hour lockdown and inmates only are allowed out of their cells once a day for exercise.

The inmates in the unit are secure in their cells and the other inmates in the prison are quiet, Ms. Morgan said.

The Department of Corrections hostage negotiation team has been summoned, she said. Units of the Oklahoma Highway Patrol, the Pittsburg County Sheriff's Department and McAlester police were assisting.