A spokesman from Shaw Healthcare on behalf of the home said the allegation was being taken "extremely seriously".
Members of staff connected to the incident have since been suspended, pending the outcome of a police and our own investigation.
We acknowledge the anxiety and distress that this has caused the resident and their family and we also wanted to have the opportunity to reassure the other residents and families so have held meetings to update them on the situation and let them know that we are taking the matter extremely seriously."
A previous CQC inspection of The Granary highlighted some areas for improvement, but the care home owners say it is "unrelated to the current situation."
More top news
A petition has begun to keep a community hospital open 24 hours. Jordan Taylor died outside Trowbridge Hospital after being stabbed
Double Olympic gold medal winner Helen Glover and her husband, wildlife presenter Steve Backshall, tell us about their next adventure
It was very pleasant today but variable cloud is expected to develop over night leading to a rash of showers come morning.