Two ambulance workers have been arrested over the deaths of six adults, police have said.
The investigation was launched in 2023 and last year a man in his 30s, from West Wiltshire, was arrested on suspicion of six counts of gross negligence manslaughter and four counts of ill-treatment or wilful neglect by a care worker.
A 59-year-old woman was also arrested on suspicion of gross negligence manslaughter in March this year. Police have only released details of the investigation and arrests now.
The two South Western Ambulance Service workers have been released on bail, Wiltshire Police said.