The fire that consumed beloved Sandy River diner Shirley's Tippy Canoe last month has been deemed "suspicious" by fire investigators.

The restaurant, located along the Columbia River Highway in Troutdale, burned to the ground early in the morning on Jan. 17. The damages exceeded $1 million and are considered a total loss.

The cause of the fire has not yet been determined, but according to a press release from Corbett Fire District 14, there were "several unusual circumstances that occurred in the days and hours leading up to the fire." The details are not being disclosed to the public.

"Those circumstances don't point us to the cause of the fire necessarily," says Corbett fire chief Dave Flood, "but they create some confusion as to what did happen."

As reported by The Oregonian, several of owner Shirley Welton's other businesses have incurred fire damage in the past, most recently Shirley's At the Beach in Lincoln City in 2011. None of these previous incidents were considered "suspicious" by investigators, however, and Flood says they do not factor into the current investigation.

Welton, 82, purchased the restaurant, which opened in the 1940s, in 2007. She told WW news partner KATU that she learned of the fire through a news report.

Flood says the degree to which the fire decimated the building will make the investigation especially challenging.

"It'll likely take weeks, probably months, and potentially go into years," he says.