A care worker has been arrested and four other employees are being investigated over allegations that an elderly female resident was assaulted at a residential home in north London.
A 30-year-old man was detained after claims of "a serious incident" at Ash Court Care Centre in Kentish Town, a spokesman for the home said.
The man has been suspended and an internal inquiry has been launched.
The home said it acted immediately and called the arrest "an immense shock".
It stressed the Ash Court Care Centre had consistently achieved the highest three-star "excellent" rating from the Care Quality Commission and had been regularly praised for its standards.
The Metropolitan Police said the elderly woman did not require hospital treatment.
Its officers were working with Camden Council's adult social care unit to "safeguard this resident and other residents", it added.'Naturally concerned'
The council said it had been informed of "disturbing allegations" about the home.
And Councillor Pat Callaghan, Camden's cabinet member for adult social care, said she and her colleagues were "naturally very concerned" about the claims of an assault.
Safety arrangements for residents at Ash Court Care Centre were now being reviewed, she said.
The spokesperson for the home said "the dignity, health and wellbeing of the people we support at Ash Court remains our number one priority".
"We continue to work closely with the family and the appropriate authorities, and will not hesitate to act immediately to safeguard the people we support," they added.
The arrested employee was released on police bail until 19 July.