LOS ANGELES, CA - For the first time in state history, California's prisons are teetering on the edge of maximum capacity.

Many of the state's 33 prisons already house two and three times the number of inmates they were designed to handle. However, when the inmate population reaches 173,000 in the upcoming months, the state will be officially out of places to put them, said Terry Thornton, a California Department of Corrections and Rehabilitation spokeswoman. The number now stands at 171,527 inmates and is growing faster than state officials had planned.

At the California Institution for Men in Chino, 42 inmates slept outdoors Thursday, refusing to spend the night in the holding tanks, a series of van-size cages indoors.

The problems caused by this population explosion at Chino alone are on track to cost the state approximately $17 million in overtime annually and raise the issue of safety for prisoners and employees alike.

In other unusual signs of crowding, the California Institution for Women, also in Chino, has begun housing 144 women in TV rooms for the first time.

It's the same story all around the state, Thornton said.

"Maximum capacity is when you're triple bunking all the cells, putting beds in the dayrooms and gyms, and you've put inmates in all the places you can think of," she said. "We can't put out the no-vacancy sign, yet there is a limit to all the people you can absorb. We're reaching that limit."

From modular housing units to community-based drug centers for nonviolent female offenders, state officials are looking at a number of ways to deal with the crowding, but nothing has been approved yet, Thornton said. Gov. Schwarzenegger's State of the State address in January described a 10-year, $14.8 billion plan to add 83,000 new beds to state prisons and county jails throughout the state.

Last year and about 5,000 inmates ago, John Dovey, the state's director of adult institutions, released a department memo warning: "This historic population high has caused significant population pressures resulting in public safety concerns ... we believe that an imminent and substantial threat to public safety exists requiring immediate action."