Four of the Massachusetts five prison guards hurt Wednesday night at Souza-Baranowski Correctional Center have been released from the hospital.

A fifth correction officer is still being treated at a hospital for non-life-threatening injuries, according to an update from around noon on Thursday from the Executive Office of Public Safety and Security.

Shawn Jenkins, the interim commissioner of the Massachusetts Department of Corrections, said in a statement that he is “deeply concerned about the incident.”

“Our correction officers perform an essential and difficult job. Their safety is our top priority,” he wrote in the statement. “My thoughts are with the officers and their families at this time and the Department offers our full support to the officers as they recover from their injuries.

“Violence against DOC staff is unacceptable, and we will take the steps necessary to ensure those responsible are held accountable under the law. Our Department will also conduct a thorough security assessment and review of protocols to ensure the safety and security of all who work and live at our facilities,” he added.

The DOC is responding with “a comprehensive investigation” alongside the Worcester County District Attorney’s office, the department said, as well as “a full security assessment.” The prisoners they say were involved have been transferred to other prisons.

The DOC heard at around 6:20 p.m. Wednesday that multiple correction officers had been injured inside the maximum-security Souza Baranowski Correctional Center in Shirley. In all, five officers were injured: two suffering from stab wounds and three more injured in some way — authorities have not disclosed what other injuries — while responding to the fracas.

The correction officers’ union reported that 38 “homemade sharpened weapons” which are commonly called “shivs,” were found inside the prison last month, the Herald reported, and have called for enhanced safety measures.