By Eric M. Johnson and Nia Williams

CALGARY, Alberta (Reuters) - Two days after the Fort McMurray wildfire turned Bruce Thompson's mobile home into a pile of ash and rubble, he called his insurer to report the damage, despondent as he discussed a life's worth of possessions gone in seconds.

The broker made the situation worse. Insurance would only pay him roughly C$60,000 ($46,959) for his possessions, about a third of the appraised value. As if to console him, the broker said there were "numerous people" like him - all under-insured.

Thompson's mobile home is among more than 2,400 properties destroyed or damaged by flames, smoke, ash, mold or chemicals in Fort McMurray area in May. With industry insiders estimating losses at between C$3 billion-C$5 billion, the fire that raged over this part of western Canada could be the nation's costliest natural disaster ever for insurers.

Although evacuees only started returning to the city last week, the insurance claims process is already deepening a sense of misery for many homeowners and businesspeople starting to rebuild their lives. This comes on top of the financial hardship that many have suffered in this oil-producing region as prices have remained in a slump.

"It's wrong, it's just terribly wrong," said Thompson, a 57-year-old heavy equipment operator. "They are trying to cut me a check and I am not taking it, I am getting legal advice."

Many residents cited insurance representatives who shocked them with lower-than-expected property appraisals, or long wait times for damage inspections by company claims adjusters.

TW Insurance Brokers Inc, who sold Thompson his Aviva Canada insurance policy, would not discuss particular claims, but said that a property loss is determined by the type of policy the homeowner has purchased and a policy can provide replacement coverage or cash at the time of the loss, with depreciation factored in.

Aviva Canada declined to discuss the situation but said it was "very much focused on our customers affected by the fires and being there for them when they need us most."

Matthew Thompson, a 32-year-old local tire shop owner who has been sleeping on a cot in his store for more than four weeks, said his insurance company, Wawanesa, threatened to cut his disaster relief stipend if he returned to his house before an adjuster assessed the damage.

"I am a hardy individual, but hearing that my young children have to stay away, and I have to keep working, it's something I am not used to," said Thompson. "I am used to seeing my family every day, at the end of the day."

The Wawanesa Mutual Insurance Company said it would not comment publicly on a specific claim, but added, "we are committed to faithfully fulfilling all terms of the insurance contracts we have in place" and are "particularly sensitive" to the needs of clients in the Fort McMurray area.

FAST DAMAGE, LONG WAITS

It often can take weeks or months to complete an insurance claim depending on the complexity of a case. Dozens of insurers with exposure in the area have taken steps to ensure an efficient process, such as bringing more than 800 adjusters and creating makeshift information centers in the city, said Bill Adams, a vice president at the Insurance Bureau of Canada, a trade group.

"Every insurance company has a well-established plan for a disaster, but this one is on a scale that's unprecedented for the industry," Adams said. "For the complete rebuilding process, you'll measure that in years, not weeks or months."

Several residents said their claims are off to a smooth start. George Avgoustis, a Fort McMurray grocer whose store had puddles of melted ice cream seeping into the aisles and rotten meat oozing out of packaging at the start of a two-week cleanup, said his experience has been good, at least so far.

"We have lawyers handling, and they say the early days of insurance claims are always all smiles," he said.

'IT'S A NEGOTIATION'

Intact Financial Corp, Canada's largest property and casualty insurer, said it would suffer losses ranging from C$130 million and C$160 million, while Economical Insurance expects pre-tax fire payouts between C$35 million and C$45 million.

Other insurers with significant exposure in the region include the insurance arm of Toronto-Dominion Bank and AIG.

One way to forecast how the insurance and rebuilding process will unfold is to look to the 2011 Slave Lake fire, previously Canada's biggest such insurance disaster, exceeding C$700 million with roughly 400 homes lost.

Among those who lost dwellings was Trevor Vance, a 40-year-old chemical company manager.

Vance said residents should get estimates from local builders they trust to compete against the cheaper figures their agents find, and "take as much time as they need" to complete emotionally overwhelming tasks and paperwork. That includes compiling a list of every possession lost.

"They are not looking out for you. You feel like they are, but the more money they save, the better," Vance said.

($1 = 1.2824 Canadian dollars)

(Reporting by Eric M. Johnson and Nia Williams in Calgary. Additional reporting by Matt Scuffham in Toronto.; Editing by Alan Crosby)