A group of Massachusetts lawmakers on Thursday urged Gov. Charlie Baker to speed up efforts to reduce the population in the state’s prisons and jails amidst a growing outbreak of COVID-19.

The lawmakers, including 15 senators and 23 representatives, sent aletter to Baker asking him to push the state Parole Board to expedite hearings and reduce processing time to release prisoners.

They also asked the governor to use his authority to shorten sentences for prisoners who are sick, and those over 60, who are not considered dangerous, as well as people returned back in prison after violating parole or probation for non-criminal offenses.

“Whatever their original offenses, and whatever their original sentences, inmates throughout the Commonwealth are now in danger of suffering the ultimate penalty,’’ the lawmakers said in aletter. “The correctional officers with whom they come into contact run the same dramatic risk.”

The letter came a day after the Department of Correction announced the sixth and seventh deaths in the prison system — both men in their 70s. At least 136 of some 7,500 prisoners in the state’s 16 facilities have tested positive for COVID-19; 100 staff and medical providers also have tested positive, according to the latest state data released.

Sen. Mike Barrett, a Democrat from Lexington, said he spearheaded the letter-writing effort because he is troubled that government officials have not been adhering to a directive by the Supreme Judicial Court to speed up the process. Earlier this month, the state’s top court released a ruling directing the Department of Correction and the Parole Board to “expedite” releases in a system where social distancing is almost impossible.

“I am annoyed that the spirit of the court decision is being subverted,’’ said Barrett in an interview with WGBH News.

Nobody from Baker’s team could be reached for comment about the letter. But in a press conference on Thursday, Baker said that officials from the state Department of Correction have been working with public health officials since early March to prevent the spread of the virus.

“There’s always going to be room for improvement,’’ he said.

Elizabeth Matos, executive director of the Boston-based Prisoners' Legal Services, said she is “devasted” to hear about new prison deaths and worries that mental health in the system is deteriorating as facilities remain largely on lockdown.

The group filed a lawsuit last week in efforts to push the state to speed up prison releases, claiming the only way to slow the spread is create more space in prison in jails. She says showers and toilets are often filthy and prisoners are put in cells without confirmation they have tested positive for the virus.

“We are devastated that more of our clients are dying prematurely as a result COVID in the prisons and jails," she said, “especially because we’ve been sounding the alarms on this for about a month and a half.”