A prostitute doing time behind bars, Marcia Powell was temporarily moved one day last month to an outdoor holding pen with nothing but a chain-link-fence roof to shield her from the searing desert sun.

She lasted less than four hours.

Powell, 48, collapsed in the 108-degree heat and died at a hospital the next day, touching off a criminal investigation and bringing an abrupt end to a little-known practice in Arizona's prison system that inmate-rights activists found repellent.

Donna Leone Hamm, director of the local nonprofit Middle Ground Prison Reform, called the outdoor cages barbaric.

"There's something medieval about it," she said. "It doesn't comport with any humane or community standard that we would ordinarily think of for any animal, including a human."

Arizona's 10 state prisons have 233 outdoor cells for temporarily holding inmates awaiting transfer to punishment wards, medical units, other prisons or work assignments. All four sides and the roof of each cell are made of chain-link fence. Some have coverings that provide shade; others do not.

They have been used year-round, despite temperatures in Arizona that can climb over 100 from the spring through the fall, and top 110 in the summer.

Corrections spokesman Barrett Marson said Arizona prisons have had outdoor enclosures since at least the 1960s. Corrections Director Charles Ryan said he does not know whether other inmates have died or become seriously ill from being held in one.

After Powell's collapse at the Perryville state prison outside Phoenix on May 19, Ryan all but banned the use of outdoor detention cells, putting Arizona in line with other hot-weather Sunbelt states. He said the cages will be used only in extraordinary circumstances, such as a prison riot or a brawl.

"The situation that Marcia Powell experienced will not occur again," Ryan said.

Florida and New Mexico do not have outdoor holding cells, prison officials there said. Texas and California have outdoor cells, but they are shaded, officials said.

On the day she collapsed, Powell, who was serving a more than two-year sentence and had a history of drug addiction and mental illness, was being transferred from one section of the prison to an observation ward after seeing a psychologist, officials said.

She was put in the unshaded holding cell and forced to wait because of a disturbance in the observation ward, authorities said.

Prison policy called for inmates to be removed from outdoor cells after two hours, but that wasn't done. Also, guards were 20 yards away in a control room while she was in the cell and were supposed to check on her every 30 minutes. Authorities are investigating whether that was done and how much water Powell was given.

A deputy warden and two guards have been suspended during the investigation.

Authorities said Powell died of heat-related causes, but the autopsy results have not been released. Investigators said they were looking into whether she was taking any psychiatric medication that might have affected her ability to withstand the heat.