A 33-year-old man arrested in relation to alleged mistreatment at Muckamore Abbey Hospital has been released on police bail.
Detectives from the PSNI's Public Protection Branch detained the man in the Antrim area on Monday morning.
He was released yesterday on bail pending further enquiries.
His was the third arrest since October. No charges have been made to date.
The Co Antrim hospital, which cares for adults with severe learning disabilities, is at the centre of the biggest police adult safeguarding investigation of its kind.
More than 300,000 hours of CCTV footage is being examined by a specialist team of officers.
