The house on Cambridge Drive, Greenfields started at around 3.30pm with 80 percent of the home damaged.

Mandurah and Falcon firefighters were called and the fire took 30-40 minutes to control.

Mandurah fire station officer Mark Lawsen said the fire started after the fan and motor overheated in the evaporative air-conditioner.

“People are reminded to not leave the house with an evaporative air-conditioner on and to not leave the area closed up as the inside of the house pressurises and puts more pressure on the motor and fan,” Mr Lawsen said.

The owners of the house were overseas when the incident occurred and people were occupying the house while they were away.

The house was insured.

On a separate incident two skip bins were set alight on Saturday at12.30am and 3.45am in Greenfields and Mandurah.

The bin on fire on Mandurah Terrace was close to a light post.

A small grass fire was started on Pinjarra Road at around 4.30pm Sunday and children were seen running from the scene.

Anyone with any information can call Mandurah Police on 9581 0222.