SHIRLEY, Mass. (AP) — Three guards were injured and a maximum-security Massachusetts prison was placed in lockdown Friday after a group of inmates attacked a guard.

State prisons officials say the officer was surrounded and then assaulted in a general population housing unit at the Souza-Baranowski Correctional Center in Shirley.

The officer radioed for help and additional officers responded and within minutes secured the area.

Six inmates were removed from the unit. Three guards, including the initial target of the attack, were taken to the hospital.

Lockdown means inmate movements and visits are restricted.