Negotiators tried to talk two inmates into freeing a pair of prison guards held hostage in an observation tower Monday for a second day.

The guards sent word that they were not seriously hurt. But authorities would not say whether the inmates had made any demands or threats, and would not disclose whether they were armed or why they were in prison.

"The conversations have never broken off," said Cam Hunter, a state Corrections Department spokeswoman. "They're back and forth, and there is a good rhythm going."

The 4,400 other inmates at the medium- to high-security Arizona State Prison Complex-Lewis (search) were locked in their cells.

The standoff began Sunday morning after an inmate attacked a guard in the prison kitchen. The prisoner and another inmate then got into an observation tower where the two guards were stationed.

Officials said it was unclear whether the standoff resulted from an escape attempt.

Two officers and a staff member were injured by the inmates, authorities said. Phoenix Fire Department spokeswoman Rebecca Dauer told The Arizona Republic that one person was severely hurt.

The two captives were allowed to speak with negotiators and reported they were not seriously injured, Hunter said.

"It's positive that the inmates allowed us to talk to the officers," Hunter said. "It's assuring for the families, for the correctional officers, for the community."

Earlier this month, unrest broke out among about 80 inmates at the prison west of Phoenix (search). Three guards suffered minor injuries and two small fires were started.

The Corrections Department last dealt with a hostage situation in 1973, when inmates killed two staff members at a state prison in Florence, Hunter said.