Police have referred an 11-year-old boy to the Whanganui Youth Aid section for allegedly starting a fire under an empty house on Kauri St on Monday night.
About 9.30, firefighters were called to a house fire at 9 Kauri St.
A Fire Service spokesman said the fire was put out quickly after reports were received of someone causing it.
The house had been vacant for several months.
Police investigation showed black polythene, laid on the ground in the crawl space beneath the house, had been set alight. An area of about six square metres of the polythene was burned. No damage was caused to the house.