POST FALLS - Investigators and accelerant-sniffing dogs on Friday started to sift through the fire debris in hopes of determining the cause of Thursday's fire that destroyed a mansion on the Spokane River in Post Falls owned by a couple whose financial woes had piled up.

"We're now digging through trying to determine a cause - however long that takes," said Dan Ryan, a division chief of Kootenai County Fire and Rescue. "With that much damage done, it may take several days. We don't know anything yet and the investigation continues."

The 11,000-square-foot, $1.5 million home at 1504 E. Plaza owned by Len and Pam Wallace was slated to foreclosure on Friday, the day after the fire. The two have gone to bankruptcy court multiple times to protect their assets.

Wallace, who on Thursday said he was close to staving off foreclosure, speculated that the fire may have been associated with one of seven fireplaces in the home. He said no one was home when the fire started.

KCFR and Post Falls police are collaborating on the investigation.

"That's not uncommon when you look at this much dollar loss," Ryan said. "We want to make sure all the bases are covered and we get the right outcome."

Accelerant-sniffing dogs assisted investigators in searching the home, "but we didn't find anything we're excited about," Ryan said.

"There's a couple things (the dogs) hit on that we ruled out," Ryan said. "They're sniffing for petroleum, but just because something had petroleum in it doesn't mean it was used as a flammable."

Post Falls Police Capt. Greg McLean equated it to a drug dog working in a pharmacy, a bit of a shot in the dark, but a tool nonetheless.

Ryan said the scene will likely be secured until Tuesday, the earliest the State Fire Marshal's Office can assist in the case.

"We want to bring in additional resources," he said.

Ryan said investigators didn't start looking through the ashes until Friday because the structure was unsafe to do so on Thursday.

"By the time we got the fire out (Thursday) it was nearly dark, so we just maintained security overnight and went back to work (Friday)," he said.

The Wallaces said no one was home when the fire started because the water had been shut off due to water damage from a dishwasher. Len said the family had been moving belongings from the home recently - as reported by neighbors - due to "an unstable situation."

McLean said the Wallaces along with their two male teens who lived in the home were interviewed and all of their testimonies as to the circumstances before the fire were consistent with each other.

The Wallaces have lived in the house built in 1986 next to the so-called Amway house once used to award those who performed well for the household products company.

The couple formerly owned the guest house on the property of the burned home before it was lost to foreclosure. Both it and the Amway house were spared from the fire.

Police responded to the home on Wednesday night after a 911 hangup call. Officers said there had been a verbal dispute between the Wallaces over keys and the dishwasher, but found no crime had been committed. Len had left before officers arrived.

Wallace said he was a victim of what he believes was a business fraud in Montana. He said he invested in a company that has products that identify dairy cows and, after he tried to get out and get his money back, there was a judgement against him.

The decision in 2003 awarded MagTrac Bolus, LLC, a $2.5 million judgement against Wallace for damages. Wallace then had five unsuccessful appeals to the Montana Supreme Court.

Wallace had plans to develop about 900 acres of property south of Post Falls on Blossom Mountain known as Raspberry Ridge until the economy went in the tank.

Wallace operated the controversial Big Velvet Ranch in the 1990s south of Darby, Mont. It was an enclosed 2,000-acre elk farm used for "shoot for pay" hunting.