A 42-year-old woman arrested over alleged abuse of patients at Muckamore Abbey hospital has been released, pending a report to the Public Prosecution Serivce.
She was detained in Antrim on Tuesday morning by detectives from the PSNI's Public Protection Branch.
It comes after a 52-year-old woman was arrested last week over allegations of ill-treatment of patients at the county Antrim facility.
In April, the Public Prosecution Service decided to prosecute seven people over alleged ill-treatment of patients there.
The facility, which is at the centre of an ongoing major police operation, treats patients with severe learning difficulties and mental health problems.