HARTFORD, Conn. (AP) — Connecticut officials voiced surprise on Monday at the extent of abuse that took place at the state’s only maximum-security psychiatric hospital, telling lawmakers they’re working to understand how it happened without the knowledge of higher-ups.

Department of Mental Health and Addiction Services Commissioner Miriam Dephin-Rittmon, referring to abuse of a patient at the Whiting Forensic Division of the Connecticut Valley Hospital in Middletown, said it’s “very troubling” that 37 staff members have been implicated and that abuses weren’t reported.

“We are working very hard to understand how this could happen and what other measures we should take to ensure this will never happen again,” she said.

Ten employees have been arrested and seven fired in connection with the case. An internal investigation is continuing, and Dephin-Rittmon said additional disciplinary actions may be taken.

Whiting’s chief operating officer and director of nursing have been removed, while an outside security firm has been hired to monitor live camera feeds around the clock. A former top Whiting official has been named acting director, and a behavioral health consulting group has been hired to help identify and rectify systemic issues, Delphin-Rittmon said.

The commissioner, who has held the agency’s top job for two years, appeared Monday at a public hearing organized by the General Assembly’s Public Health Committee when the legislature is not in session. Lawmakers are expected to consider possible reforms when they reconvene in February.

Delphin-Rittmon said she believes fear and intimidation contributed to why the abuse continued without the knowledge of top Whiting officials. A recent state Department of Public Health report found staff members put a diaper on a patient’s head, threw food at him, poured water over him, put salt in his coffee, kicked him and placed a mop on his head after cleaning a floor.

The report also found the 62-year-old patient had been kicked, jabbed, poked and taunted by staff over several weeks this year.

The Department of Public Health investigated at the request of the federal Centers for Medicare & Medicaid Services, which regulates the hospital, following a whistleblower complaint.

Delphin-Rittmon said video evidence of the abuse “has sickened and haunted” her since she first watched it.

Whiting is part of Connecticut Valley Hospital, a psychiatric care complex run by the Department of Mental Health and Addiction Services. It includes 106 beds for patients in maximum security and 141 beds for those in enhanced security. The patients include people found not guilty of murder and other crimes by reason of insanity and other people committed voluntarily or involuntarily by civil courts.

State Sen. Heather Somers, the Republican Senate chair of the Public Health Committee who pushed for Monday’s hearing, said she believes the state needs to do more to address a systemic problem of bullying and fear of retaliation among employees.

“They have not been supervised, clearly, when this has been allowed to happen,” said Somers, of Groton. “I really feel that we need to find out where the system has broken down before we can fix it.”