SACRAMENTO — The federal three-judge panel that previously set a population cap for the California prison system has rejected an effort by activists to require further inmate releases to slow the spread of the coronavirus behind bars.

In an order filed Saturday evening, the judges ruled that they did not have authority to consider the request because the panel had originally been convened to address a different issue: prisoners’ lack of access to adequate medical and mental health care. Advocates said they would pursue their motion in other courts.

“We take no satisfaction in turning away Plaintiffs’ motion without reaching the important question of whether Defendants have implemented constitutionally adequate measures to protect the inmates of California’s prisons from the serious threat posed by this unparalleled pandemic,” the judges wrote.

In a separate but related matter, California’s Judicial Council, which sets policy in state court, was scheduled to hold an emergency meeting on Monday to vote on nearly a dozen temporary rules, including a proposal to lower bail to $0 for misdemeanor and lower-level felony offenses, the Associated Press reported. The measure is aimed at reducing the prison population and halting the spread of the coronavirus.

Also among the council’s proposed rules is conducting criminal and juvenile proceedings by video or telephone. The move is designed to ensure that defendants get timely hearings.

While the federal judges over the weekend did not take up the request to expedite releases, they said that advocates could instead seek relief for inmates before their individual courts, which could then potentially order other safety measures. If those measures proved inadequate to protect prisoners, the three-judge panel could reconsider a release order. Each of the judges is from a different federal court.

“We recognize the deference that is due to prison authorities to determine which additional measures must be taken to avoid catastrophic results,” the judges wrote.

The number of infections in the prison system is relatively low, but growing. The corrections department has reported 60 confirmed cases: 47 staff members across the state and 13 inmates, mainly at the prison in Los Angeles County.

Advocates fear that, without drastic measures to allow for social distancing, the virus could tear through overcrowded dormitories where inmates share cramped bunk beds and bathrooms. The prison system is currently operating at nearly 134% of its design capacity, slightly below a population cap of 137.5% mandated by the three-judge panel in 2009.

Attorneys representing inmates filed their emergency motion last week asking the federal judges to order the release of thousands who are most vulnerable to the virus because of their age or underlying medical conditions and those nearing the end of their sentences.

Michael Bien, one of the lawyers, said Saturday that he did not consider the order a defeat, because “all three judges seemed to be very much in agreement with us” that the spread of the virus in the prisons is a crisis.

He said they will continue to pursue their motion before the individual judges, but “it’s our hope that the governor and other state officials reading this opinion will see the message is very clear” and act on their own.

The California Department of Corrections and Rehabilitation said Tuesday it would review up to 3,500 inmates for early parole if they are within 60 days of their earliest possible release and were not convicted of a violent offense.

That follows an executive order last month by Gov. Gavin Newsom suspending prison intake, which the state said could reduce the prison population by about 3,000 people over the next month. There were 113,643 inmates Wednesday, down 524 from the week before.

“The order speaks for itself,” Dana Simas, a spokeswoman for the corrections department, said in email Saturday, “but CDCR has taken significant steps to address the safety and well-being of inmates and staff during the COVID-19 pandemic.”

Corrections officials have also canceled regular family visits, added hand sanitizer dispensers to common areas, and begun screening the temperature of everyone who enters the prisons.

Alexei Koseff is a San Francisco Chronicle staff writer. Email: alexei.koseff@sfchronicle.com Twitter: @akoseff