Police have raided a methamphetamine laboratory in a small settlement near Nelson.
About 40 staff, including P-lab specialists from Auckland and Wellington, were involved in the operation, in Wakefield.
Equipment and chemicals have been seized.
A 37-year-old woman and a 32-year-old man have been arrested.
Detective Inspector Brett Greer says it's concerning that three young children were living in the houses.
He says other arrests are possible.