Police are urging tradespeople to increase security on Christchurch building sites following a spate of thefts at the Pegasus subdivision at the weekend.
They say thieves stole three heatpump units and copper piping from 13 houses under construction on unfenced sections on Infinity Drive.
Detective Senior Sergeant Corrie Parnell says locked fences are a good deterrent, as is contractors timing deliveries so valuable appliances aren't left unsecured and unattended.
Mr Parnell says the thieves would have needed one or more large vehicles to transport the stolen items, and may have looked like genuine tradespeople.
He says the number of thefts from residential and commercial building sites throughout Canterbury is increasing and is appealing for any information from the public.