CALGARY, Alberta (Reuters) - A war on gophers waged by two Canadian men went awry this weekend when a device used to blast the rodents in their holes sparked a massive grass fire in a rural area near Calgary, Alberta, causing more than C$200,000 (99,000 pounds) in damages.

Despite a ban on fires in the tinder-dry area of Springbank, just northeast of Calgary's city limits, two men went into a field to kill gophers using a device called a Rodenator, fire officials said on Monday.

The device pumps a mixture of propane and oxygen into gopher holes, which is then ignited, and, according to the manufacturer's Web site, the resulting blast creates a shock wave that kills the gopher and collapses its tunnel system.

"We had a couple of acreage owners out taking care of their rodent problem with this device," said Captain Joe Garssi of the municipal district of Rocky View's fire department.

"They did a few holes successfully and then hit a hole that didn't go in very far. When they filled it with propane it over-filled the hole...and when they ignited it (fire) flashed out of the hole into the grass beside them."

The resulting grass fire scorched about 160 acres of surrounding property and destroyed a number of outbuildings. No homes were damaged.

"The way I look at it, it's 'humans eight, gophers one'." Garssi said, as the two men destroyed about eight of the rodents before sparking the blaze.

Charges are being considered against one of the two men involved.

In Western Canada, gophers, more properly called Richardson's ground squirrels, are often considered a nuisance, blamed for ruining crops and damaging golf courses and lawns. ($1=$1.02 Canadian)

(Reporting by Scott Haggett; Editing by Peter Galloway)