The Alberta government now believes a fire that caused about $700 million in damages after sweeping into Slave Lake on May 15 was deliberately set, and has turned over its files and reports to the RCMP.

“Our investigation into the origin of that fire ruled out everything but arson as a probable cause,” Sustainable Resource Development Minister Frank Oberle said Tuesday. “As a result, we have delivered our findings to the RCMP to determine if a criminal investigation is the next step.”

The investigation into the cause of the Slave Lake wildfire took five months, involving extensive onsite and offsite work to gather evidence, said Oberle.

“Our investigation took the time required to protect, collect, analyze and document evidence to the rigorous standards required for presentation in a court of law,” he said.

Province knows where fire began

The province knows precisely where the fire was set, but cannot disclose the location as it's now considered a crime scene, said Oberle.

Alberta Sustainable Development Minister Frank Oberle and RCMP superintendent Marlin Degrand speak to reporters Tuesday. CBC

The fire that burned into the town of Slave Lake and nearby Poplar Estates was one of 45 to strike the Lesser Slave Lake Area between May 13 and 16.

The 4,700-hectare fire began southeast of Slave Lake on May 14, led to the evacuation of 7,000 residents and eventually destroyed about 400 structures, mostly homes.

"It's a sick feeling. It makes you angry, more angry than before, because how can somebody do something like this?" said Myrtis Mitchell, who lost her house in the fire. She also lost her home in Newfoundland to fire last month.

The entire community is surprised and saddened to learn the fire is now considered arson, said Mayor Karina Pillay-Kinnee.

"It's disappointing," she said. "It's definitely something we thought of, but it's definitely very concerning to hear that this is a possibility now."

Slave Lake RCMP members were also shocked by the news.

As 11 officers lost their home to the fire, the local detachment will not be involved in the investigation in the interest of accountabilty, said Staff St. Roberta McKale.

The wildfire is the second-most-costly insured-damage disaster in Canadian history, behind the 1998 Quebec ice storm.

In August, the province announced an independent review of how well it fought the Slave Lake fire and the effectiveness of its fire management programs.

"We want to know how the combination of the burning conditions, the crew response...and what we can do to improve," said Oberle. "Were there any shortcomings in our actions?"

The minister expects a report early in 2012 with enough time to implement recommendations before next fire season.