Without a U.S. Supreme Court reprieve, California will have to free roughly a third of its prison inmates in a few years, and how that can be done safely is still hotly debated.

Corrections officials said Tuesday they are struggling with their response to a tentative federal court ruling this week that the state must remove as many as 57,000 inmates over the next two or three years.

The state's 33 adult prisons now hold about 158,000 inmates. But the judges said overcrowding is so severe it unconstitutionally compromises medical care of inmates, and releasing prisoners is the only solution.

"We are just now beginning to have discussions (about) who these types of inmates would be. Then, how do we get to that number?" said Matthew Cate, secretary of the state Department of Corrections and Rehabilitation.

The department has no contingency plan, he said, other than appealing to the U.S. Supreme Court once the ruling becomes final.

The judges said their ruling does not amount to throwing open the cell doors.