A police investigation has been launched into reports of assaults and ill treatment by staff at Winterbrook Nursing Home in Wallingford, Oxfordshire.
The BBC reported officers attended the service on 23 June but no far arrests had yet been made.
A Thames Valley Police spokeswoman said: “Officers are currently investigating common assault offences and ill treatment by care provider and ill treatment by care workers.”
The CQC rated the home Inadequate following an inspection in July that was prompted by allegations of the abuse of residents.
The CQC commented: “People were not always protected from abuse and improper treatment and were not confident to raise concerns. Medicines were not always managed safely and risks to people were not always assessed and managed.”
Paul Kelly, Operations Director, said the service provider “apologise unreservedly to everyone connected with Winterbrook, in particular residents and their families”.
He added: “We were outraged and saddened by the examples of abuse brought to our attention.
“All members of staff associated in any way with this behaviour towards residents were either dismissed or resigned as soon as we were notified of the behaviour.
“We have drawn up a detailed, comprehensive and robust action plan to resolve all inadequacies and we are updating the CQC on a weekly basis.”