Four people have been arrested in relation to an alleged cannabis-growing operation in Auckland.

On Friday, Counties Manukau police undertook six search warrants at properties across the city targeting the “significant” operation, Detective Inspector Chris Barry said.

One of the raids took place at a townhouse on Houkura Way​ in Sandringham​, where a rubbish skip full of growing equipment and the dregs of a marijuana crop were left behind.