Dozens of prisoner rights activists stormed Gov. Charlie Baker's office on Wednesday to demand he investigate allegations of mistreatment at the Souza-Baranowski Correctional Center in Lancaster.

The demonstration in Baker's office came after a crowded State House presentation, during which former Souza prisoner Darrell Jones suggested that the advocates bring their concerns directly to Baker.

"There's enough people in this room right now to get up and say I'm going to finish this in front of the governor's office," he said.

The group brought Baker a letter from Prisoners' Legal Services of Massachusetts calling for an outside investigation. The letter noted widespread reports of violence against prisoners after four guards were injured during a Jan. 10 attack at the prison.

The group's executive director, Liz Matos, said Baker has been quiet about the Souza controversy except to express faith in the state Department of Correction.

"We understand that he also has the power to do something here but nothing has really been done at this point except for a statement trusting the DOC to investigate itself," Matos said.

Aides in the office took the letter and promised to pass it along to Baker. They also asked organizers to request a meeting.

Among those who spoke at the presentation before going to Baker's office was Jason Schultz, who was released from Souza three weeks ago. He said he was attacked by three correction officers while he was handcuffed during the aftermath of the Jan. 10 violence.

"I was gouged in both eyes, struck with closed fist punches in my ribs and facial area, kicked in the face once and tased simultaneously as the assault continued down a hallway and into an elevator," he said.

The meeting was organized by state Rep. Chynah Tyler, who has filed bills to reform correctional policies. One would create a new Correctional Oversight Commission that would review policies for both jails and prisons.

"It's a bill to create a preventative measure to be sure that things like this are not able to happen in the future," she said.

Souza was locked down for weeks in response to the January attack on the guards, but the restrictions have since been lifted, according to department officials.

Last week a Suffolk Superior Court judge ruled in favor of Souza prisoners and said the DOC must give them appropriate access to their lawyers and legal documents — both of which were restricted during the lockdown.

In a statement Wednesday, the Executive Office of Public Safety and Security said steps were taken to secure the prison after the violence and the DOC will review all complaints.