A mouse is believed to have caused a house fire in Southland yesterday morning.

Firefighters were called to the Waimatuku Flat Rd house, near Thornbury, 30km east of Invercargill, about 1.30am, after its owners reported the heat pump on fire, The Southland Times reported.

House owner Colin Tait said he awoke to a strange light in the hallway and found the heat pump alight.

He got his family out of the house, and when he returned seconds later, the small fire had spread halfway up the wall.

Mr Tait used fire extinguisher to put out the flames before getting back outside.

Fire Service fire risk manager Paul Glanville told the newspaper an electrical fault in the heat pump, believed to have been caused by a mouse chewing through wires, started the fire.

The mouse's charred remains were found inside the heat pump.