Mr Kofoed said grates so far have been stolen mainly on the east side of the city.
He is unsure as to why people would steal them, but has a number of ideas.
"We have speculated on a few different possible uses for them ... They could be used as some sort of cooking implement because they retain heat so well, or potentially as some kind of heating device, or they may be on-sold to scrap metal dealers.
"We are heartened by the response from the social media community, and using Facebook has led to a drop-off in thefts — although of course we'd like this to stop altogether as this is costing Hamilton ratepayers money."
He said grates costs roughly $500 each to replace.
"Catchpit grates are replaced as soon as possible. If we don't have enough replacement grates on-hand, we cover the hole as a risk mitigation."
He encourages members of the public to keep an eye out for the thieves, and to contact the police.