Elderly and vulnerable residents are being warned to be vigilant after burglars disguise themselves as council staff.
Nottinghamshire Police officers are advising people not to answer the door to any unexpected callers and report anything suspicious.
The warning comes after five distraction burglaries between Saturday October 14 and Tuesday October 18, when previously there had been just once since the start of September.
The offences have happened in Forest Town, Lowdham, Cotgrave, Ollerton and Mansfield, and in each one the burglars have used similar distraction techniques, claiming to be doing official work in the area before they or an accomplice steal from their homes.
The recent cases have involved people claiming to be from the council or the water board, doing gardening or guttering work, and even checking homes after a gas explosion.
Detective Inspector Pam Dowson, from Nottinghamshire Police, said: “Our message is simple - if you are not expecting someone coming to your home, don’t answer the door. Official callers will always make an appointment in advance.
“Unfortunately these unscrupulous people tend to prey on the most vulnerable people and we would urge anyone with elderly or vulnerable relatives or neighbours to keep an eye on anyone calling at their house, where possible.
“If anyone sees anything suspicious, please call Nottinghamshire Police on 101, or Crimestoppers anonymously on 0800 555 111.”