Hundreds of prisoners in Massachusetts have been released during the COVID-19 pandemic, but a court-ordered report suggests that few in the state's jails and prisons have been tested for the coronavirus.

The report, from an attorney appointed by the Massachusetts Supreme Judicial Court, says 637 prisoners have been released from state prisons and county jails since April 5. The state's highest court ruled on April 3 that some prisoners could seek release, and that correctional facilities had to provide weekly reports on the number of people released and the numbers of those tested. Those eligible to seek release include people held awaiting trial and those incarcerated on some parole and probation violations.

Some prisoners rights advocates say it's not clear if the releases are due to the SJC ruling or if some would have happened anyway.

"It's hard to know with this data," said Lizz Matos, executive director of Prisoners Legal Services of Massachusetts. "It doesn't delineate between regularly scheduled prisoner releases and releases that occurred pursuant to the SJC order."

The American Civil Liberties Union of Massachusetts and the Committee for Public Counsel Services — the state's public defender agency — have filed a complaint against the DOC arguing that it is not providing the data required by the April 3 ruling.

The report says nine county jails have tested fewer than 10 prisoners since April 5. Some jails tested no prisoners at all during that time, including those in Barnstable, Dukes and Franklin counties. Of the 257 prisoners tested in jails since April 5, 37% — 97 people — have tested positive for the coronavirus.

The state Department of Correction reports testing 291 prisoners, with 117 testing positive. It also reports that 71 DOC and vendor staff have tested positive.

"I think it's hard to argue that we're doing the amount of testing that we need to be doing," Matos said. "We need to be testing more people to really understand the impact of the virus inside."

Statewide, more than 175,000 people have been tested, and more than 41,000 people have tested positive — a 26% positive rate.

Various legal fights continue over releasing prisoners to mitigate the spread of the disease in correctional settings. The SJC is expected to review a class action lawsuit seeking to release some of those who have been sentenced and those civilly committed to jails and prisons for addiction treatment.