Burglars raided six homes and five businesses in central Sheffield last week.
Crooks struck in Clarkegrove Road, Marlborough Road; Southgrove Road, Southbourne Road, Rutland Park, all in Broomhill; Eastgrove Road and Broomhall Road, both in Broomhall; Carver Street, Castle Square and Union Street in the city centre and Dun Street, Shalesmoor.
There was an attempted burglary in Hartshead in the city centre.
A South Yorkshire Police spokesman said: "We believe offenders have accessed the properties through insecure downstairs windows, open windows, window locks being snapped and door locks being snapped.
"All burglaries and attempted burglaries are being investigated and crime prevention advice is being given during house-to-house enquiries.
"High visibility patrols are also being increased in the area."
Anyone with information about the break-ins or offenders should call South Yorkshire Police on 101 or Crimestoppers on 0800 555111.
Visit www.southyorks.police.uk/bewise for information and advice on how to avoid becoming a victim of crime.