As news of prison staff and inmates infected with COVID-19 spreads across the United States, some local Massachusetts prosecutors and advocates are working to get the most vulnerable out.

Several officials from local district attorney offices say they are working with defense attorneys and houses of correction to identify elderly and sick inmates who merit release.

Among them, Suffolk County District Attorney Rachael Rollins on Thursday said supervisors are currently reviewing requests for release for those who “pose no meaningful risk to public safety.” She said her office is generally not requesting bail for new people charged with new offenses.

“While Americans across the country are being encouraged to self-isolate, members of our incarcerated population are, by definition, doing the exact opposite with no alternative options,’’ Rollins said in a statement. “We need to seriously consider pathways to prevent the spread of COVID-19 for our incarcerated populations, the overwhelming majority of which will return to our communities at some point in the future.”

Officials from the district attorney’s offices in the counties of Middlesex, Worcester, Norfolk and Bristol and the Northwestern district say they will review cases of inmates who may qualify for early release, WGBH News learned Thursday.

Four local prosecutors — including those in the Northwestern district, Middlesex, Suffolk and the Berkshire counties — also signed a national letter calling for a reduction in incarcerated individuals as a safety precaution and to implement long-needed reforms.

“An outbreak of the coronavirus in these custodial facilities would not only move fast, it would potentially be catastrophic," the letter said.

Concern about public safety in the state’s prison system come amidst news that staffers in two federal prisons in New Hampshire and Texas may be infected with the virus and an inmate in New York’s Riker’s Island tested positive.

Last week, the Massachusetts Department of Correction announced it would immediately stop friends and family visits to the state’s 16 correctional facilities that incarcerate about 9,000 people.

But not everybody is supporting new efforts. Essex County District Attorney Jonathan Blodgett doesn’t see any reason to proactively review new cases, according to a spokesperson. Blodgett was assured by county jail officials that, “every effort is being made to protect the health and well-being of the people in his care and custody,” said spokeswoman Carrie Kimball-Monahan.

Plymouth County District Attorney Timothy J. Cruz also doesn’t plan to proactively partake in additional reviews of inmates for early release. “We can count on the Sheriff to maintain a healthy and safe facility for people in his care and custody,’’ wrote spokeswoman Beth Stone.

Efforts to release inmates also require cooperation from the state parole board and county sheriffs who oversee the state’s jail system. Parole Officials said late Thursday that they are continuing to conduct hearings, that sentences are imposed by judges and that prosecutors and defense attorneys can seek a hearing for re-sentencing.

Middlesex Sheriff Peter Koutoujian says he is actively working with the district attorney’s office to see if some inmates can have their bail reviewed. But Bristol County Sheriff Thomas Hodgson released a statement Thursday saying he is “deeply troubled” by plans to release inmates.

“You know what’s not in the best interest of public safety?” he wrote. “Letting hundreds of people that were either convicted of a crime and are serving their sentence, or are accused of committing a crime and ordered held behind bars by a judge, walk out the front door in the middle of a public health emergency.”

Another possible complication to efforts to release prisoners is that much of the Massachusetts legal system has shut down. The state Supreme Judicial Court announced the closure of the state’s trial courts until April 6 except for emergency matters. The state’s probation service announcedplans to limit face-to-face visits with those under supervision, carrying out most business by phone.

Elizabeth Matos, executive director of the Boston-based Prisoners' Legal Services, urged government officials to move quickly. She said it’s only a matter of time before the virus infiltrates the state system of jails and prisons. Many inmates are elderly or sick in a system where even soap can be in short supply, she added.

The challenge, she said, will be to find places outside the prison to house many of the elderly inmates. But there are also those who have homes to go to, she said.

“The sick and elderly should be released,’’ said Matos. “Once the virus gets in there, they are not going to be able to treat people.”

Correction: This article has been updated to correctly spell Rachael Rollins' first name. It is Rachael, not Rachel.