Metal thieves who have been stealing copper gas pipes from outside Leicestershire homes are putting lives at risk, police have said.
Twenty homes in the Westcotes area of Leicester have been targeted by offenders recently.
Police have been offering to mark residents' property in the neighbourhood to help combat the crime.
Pipes on 40 homes have been marked with SmartWater, a clear solution that shows up under ultra-violet light.
Police community support officer Lauren Billig said: "Tampering with live gas pipes is not only dangerous to the suspect but to others living in the area.
"Property marking is easy and a good way of making property distinctive," she said.
Police said metal theft was on the increase and people should report anyone acting suspiciously and looking at metal on houses.