Two sisters and seven children had a lucky escape after their rental home accidentally caught fire in Coonamble on Thursday 12 June.

One of the sisters said an off-duty police officer noticed smoke coming from the house on Arthur Street at around 5pm and called out from the front gate since there were dogs on the premises.

"I was cooking and I had my daughter in the shower. I knew nothing," the woman said.

"She said 'do you have a fire at the back?' and I said 'no.' She said 'I think your house is on fire.'"

"It went quick. As soon as it got through the laundry, then it went through the kitchen," the other sister said.

The youngest child recently turned one.

Firefighters at the scene on Arthur Street. IMAGE: River McCrossen

Police, firefighters, SES and paramedics shortly began to arrive on scene and the blaze was brought under control by 6:20pm.

A HAZMAT team later arrived for potential asbestos contamination and the house's front fence was taped off.

Local Fire and Rescue NSW captain Andrew Morley said fireplace ashes were placed in a plastic bucket, which caught alight.

"It's probably a bit of a warning for people to be vigilant with cleaning out fireplaces. Use a metal bucket," he said.

"They may seem to be cold enough, but just be wary where you're placing your hot ashes."

He also said residents should ensure they have working fire alarms, which the rental did.

Firefighters also attended a suspicious small grass fire on the Castlereagh River near the end of Barton Street at around midnight on the same evening.