A Prince Edward Island couple has found out the hard way that potting soil is a potential fire hazard.

Emily and Will Cahill brought a planter filled with potting soil in for the winter and placed it in their basement.

They were painting a cellar door when their smoke detector went off.

"So I opened the door, and white smoke hit him right in the face," Emily said.

Will went down to investigate. The flower pot, sitting on a metal tray, "burnt the bottom right out of it. And that scared me real bad," he said.

The potting soil just seemed to catch fire on its own.

Local fire officials say a similar incident happened last year.

"It was identical, they had a plastic pot like this," said Jim Peters, fire chief in Summerside.

Spontaneous fires have been known to start in piles of hay or compost. However, many don't realize the same phenomenon can occur with potting soil.

"Its a potting soil. There may be some combustible products embedded in it, some wooded products, it could be some contaminant or fertilizer," said Dave Blacquiere, PEI's fire marshall.

There's a lot of organic matter in potting soil. If the moisture level is right, the decomposition of that organic mater can generate heat.

"I want people to know to check their basements, not to leave potting soil in their homes!" Emily said.

With a report from CTV's John Vennavally-Rao