Two washing machines which had been recalled have exploded in Waikato this week.
The Samsung top loader models were recalled in 2013 due to risk that water could get into the electrical system and cause a fire.
Fire Service fire investigations manager Peter Wilding told Fairfax when they were recalled there were about 34,000 affected machines in use.
Most of them had been recalled, but 4000 were still remaining.
"In the last four years some of those may have been tossed out," Wilding told Fairfax.
"We don't know how many are still operational. We have seen about three a month overheating and leading to fire."
Wilding said there have been 18 Samsung washing machines linked to fires this year, and 13 were linked last year.
The latest fire was in Hamilton on Saturday about 5.30pm, when the machine burst into flames.
Waikato fire investigator Peter Hallett said a neighbour saw smoke coming out of the window of the house and alerted the residents.
It was the second fire caused by a washing machine in the region in the past 10 days, after a machine in a rural area also caught fire.
Wilding told Fairfax that Samsung had gone "above and beyond" in enforcing the recall.
Those with affected machines are asked to call 0800 855 502 or go to http://www.samsung.com/nz/support/rework/.
The affected model numbers are: