The appearance of two guards on the deck of an Arizona prison (search) tower where they are being held hostage by two inmates gave negotiators hope as talks to end the standoff entered a sixth day Friday.

"It's naturally tense, but the feeling by the negotiating team is positive," Department of Corrections (search) spokeswoman Cam Hunter said Friday. "As long as it appears that the officers are still safe, we're very encouraged."

She said both guards, a man and a woman, said they were OK.

Later in the day Friday, one of the inmates was seen walking onto a third-story observation deck and using a rope to pull up a round orange cooler. Reporters also saw the inmate pull up another object, possibly another cooler, but Hunter wouldn't discuss what was going on.

On Thursday, each of the guards was allowed to walk up a set of stairs and onto the tower's observation deck during a "critical juncture" in the negotiations, said Yuma prison warden Ivan Bartos, who is assisting negotiators. He declined to elaborate.

Also on Thursday, one of the inmates appeared on the observation deck of the three-story tower and looked over the side, Hunter said. She said the inmate may have been there to verify that the situation outside was as negotiators had described it.

A day earlier, one of the inmates had set off a gas canister that landed in a prison yard. No one was injured and the negotiations continued.

The guard tower, in a yard for high-security inmates, is believed to be stocked with weapons.

Authorities have not released details of the negotiations, including whether the inmates have made specific demands or any threats. They also haven't discussed why the inmates may have taken the two guards hostage.

"It's difficult to understand, and pointless to speculate, what they were thinking, or what the inmates want," Bartos said.

The standoff began Sunday morning after an inmate attacked two guards and a worker in a kitchen area. That prisoner and another inmate then got into an observation tower where the two guards were stationed. The identities of the inmates and guards have not been released.

The rest of the prisoners are in lockdown at the Arizona State Prison Complex-Lewis (search), a 4,400-inmate medium- to high-security prison west of Phoenix. Bartos described the mood inside as subdued.