Mystery surrounds a review launched at the Bupa-run St Mark's Nursing Centre that has also seen three nurses suspended.
The Royal Borough, Care Quality Commission (CQC) and Bupa are working together on a joint probe into 'quality of care' but none have provided any further details.
The borough, which is responsible for social services across Maidenhead and Windsor, said the centre's Henley Suite rehabilitation unit is the focus of the review but it would be 'unfair' to discuss details.
Bupa suspended new admissions to the home in St Mark's Road from Thursday, October 24.
Company spokesman Graham Brittain said: "The health and wellbeing of our residents is always our absolute priority."
The care home is split into four houses, which provide elderly nursing care, rehabillitation services and dementia care.
The CQC was unavailable to comment.
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