The investigation into Thursday's fire that destroyed a Post Falls mansion on the Spokane River will resume on Tuesday.

An investigator from the State Fire Marshal's Office will join the investigation to assist Kootenai County Fire and Rescue, said KCFR Division Chief Dan Ryan.

Ryan said he's also requested help from the federal Alcohol, Tobacco, Firearms and Explosives agency, but hasn't heard back as to whether it will assist.

A security company guarded the scene over the weekend and today during the Presidents' Day holiday. Petroleum-sniffing dogs were called to the home on Friday and, while some samples were sent to a lab, Ryan said there were no obvious hits that pointed toward arson.

The 11,000-square-foot home at 1504 E. Plaza, which was assessed at $1.5 million, has been owned by Len and Pam Wallace for the past 10 years.

It was slated to be foreclosured upon on Friday, the day after the fire. The Wallaces have gone to bankruptcy court multiple times to protect their assets.

Len Wallace speculated the fire may have been associated with one of seven fireplaces in the home.

There were no injuries.