Dozens of drain covers have been stolen from streets around York, in what has been described as an "incredibly dangerous act of vandalism".
More than 50 metal gully grids were taken from the New Earswick area of the city on Tuesday.
North Yorkshire Police said a white van was seen "acting suspiciously" in the area at about 07:00 GMT, and have urged witnesses to come forward.
City of York Council said staff had been deployed to make the areas safe.
The covers were taken from Willow Bank, Poplar Grove, Station Avenue, Hawthorne Terrace South and Hawthorne Terrace North.
James Gilchrist, the council's assistant director of Transport, Highways and Environment said: "This is a shocking and incredibly dangerous act of vandalism.
"This theft is one of the most selfish we've encountered.
"Not only is this a serious danger to the public, it's taken additional resources, time and money to replace covers, at a time when our crews are already stretched."