Nottinghamshire Police said officers were investigating whether any criminal offences had taken place at the care home.
A spokeswoman said: "A police investigation has been launched after concerns were raised about the standard of care provided to residents at Autumn Grange in Sherwood Rise."
Police will be speaking to former residents and their families and will work closely with partner agencies to establish if any criminal offences have taken place."
More top news
So-called legal highs are set to be banned en masse. But what are they, and why is this drastic move necessary?
The Swiss 79-year-old joined Fifa in 1975, with his reign as president starting in 1998. But who is he?
85% of products surveyed by the charity Action on Sugar were found to have more of the sweet stuff than Haribo.