An eighth person has been arrested by detectives investigating allegations of ill-treatment of patients at Muckamore Abbey Hospital in Antrim.
The 57-year-old woman was detained on Monday morning in the Antrim area. There are no further details at this time.
Muckamore Abbey houses patients with severe learning disabilities and mental health issues.
Allegations of abuse of patients at the facility, which first emerged in 2017, have resulted a major police investigation and 59 precautionary suspensions of staff members, however no one has been charged.
Detectives have viewed thousands of hours of CCTV footage from the hospital as part of their investigation.
The Department of Health last month published a damning review into the leadership and governance at Muckamore, covering the period from 2012 to 2017.
Health Minister Robin Swann apologised on behalf of the health service to patients and their families who he said had been "let down".
Mr Swann said he would be establishing an inquiry into the allegations of abuse at the hospital.
"This was a sustained failure of care, affecting some of the most vulnerable members of our society," he said.
"Patients and families have been let down and I want to apologise to them on behalf of the health and social care system."