Brazen thieves have stolen nearly 100 storm water grates from Manukau, New Zealand city streets in the past month.

Now the Manukau City Council is asking the public and scrapmetal companies for help in trying to stop the thefts, according to a report in the Manukau Courier.

The grates seem to have been stolen mainly in areas where inorganic rubbish is sitting by the road waiting to be collected.

Replacing the cast iron grates will cost the council about $15,000.

Council transportation manager Chris Freke believes they are being stolen for their scrapmetal value.

"The scale of it is a bit disturbing," said Freke.

The grates typically weigh 20kg each and more than 90 have been taken in Manukau in the past month.

"It looks as if they are using the guise of the inorganic collection to have trucks going past and they are pulling out the storm water grates as they go through."

Freke said a truck is probably being used and the thieves are likely to be in the trade and working with "some nefarious scrap dealer".

An Auckland region scrapmetal company spokesman said the thieves might not be making a huge profit.

His company pays about $100 a ton for cast iron but other companies might pay more.

Source: Manukau Courier