State safety regulators have launched an investigation into an assault at the Minnesota Security Hospital that left a staff member hospitalized with serious injuries.

Officials with Minnesota OSHA, the state workplace safety agency, made a surprise visit last Thursday to the security hospital in St. Peter, following a report that a 16-year-old patient grabbed a security counselor by the hair, bashed her head against a wall and kicked her in the head repeatedly.

The assault is the latest in a recent string of violent attacks on staff at the state's largest psychiatric hospital, which houses about 225 of Minnesota's most violent and mentally ill patients.

State OSHA investigators met with security counselors on the hospital unit where the attack occurred, according to hospital staff, and asked questions about what may have triggered the violence.

"It's clear they are dissecting this very closely," said Tim Headlee, a security counselor at the hospital and president of AFSCME Local 404, which represents about 500 workers at the hospital.

The state's failure to bring violence under control at the security hospital has drawn the attention of Gov. Mark Dayton. On Tuesday, Dayton's chief of staff, Jaime Tincher, will tour the facility along with several state lawmakers, including the head of the legislative committee that oversees the hospital.

"The administration is actively engaged in finding solutions that will ensure the highest possible safety standards for both workers and patients," said Dayton spokesman Matt Swenson.

Staff at the mental hospital have suffered 68 work-related injuries so far this year, a pace set to easily exceed last year's record of 101. And at least two hospital workers have suffered concussions from patient assaults this year, according to state OSHA records.

"Workers at the security hospital feel like getting hurt has become part of the job description," said Jennifer Munt, a spokeswoman for AFSCME Council 5, which represents 790 workers at state-operated facilities in St. Peter.

The state Department of Human Services has taken measures to improve safety since late last year. This includes installing new cameras in the high-acute units and common areas; establishing a four-bed admissions unit to protect new patients from more violent ones, and buying protective equipment, such as body and forearm pads for staff.

The agency is working to fill 20 security counselor positions and 24 other positions.

Workers at the hospital said efforts to decrease assaults have been hampered by rules that limit the use of restraints and seclusion, as well as a new state law that has forced mental hospitals to accept more patients with criminal histories who may be more prone to violence. The Legislature passed a law in 2013, known as the "48-hour rule," that requires state facilities like the security hospital to admit county jail inmates within 48 hours after being committed by a state judge as mentally ill.

The hospital needs to hire another 54 security counselors to be fully staffed, 24 hours a day, say AFSCME officials. The union also wants the hospital to bring back so-called "mobile restraints," which allow patients to be able to walk and eat but prevent them from hitting others.

Hospital staff currently can use restraints and seclusion only when a patient poses an "imminent risk" of causing harm to self or others. This limitation often means that staff feel they cannot respond until after they have been assaulted, Headlee said.

In the most recent incident, workers noticed that the unidentified teenage patient was agitating other patients several hours before the assault. Counselors escorted him to the hospital courtyard to prevent him from injuring other patients. But as soon as they reached the courtyard, the patient grabbed the female security counselor by the hair and bashed her head against the wall, union officials said.

The staff member was taken to the Mayo Clinic in Mankato and is now recovering at home.

"There are no consequences for aggressive behavior inside the hospital," Munt said. "And until there are consequences, patients won't be ready to return to the community."