A 2,500-acre fire burning on the Kenai Peninsula about 30 miles north of Homer started when sparks from a grinder being used to sharpen a shovel fell into dry grass, Division of Forestry officials said Wednesday.

The Caribou Hills fire in a popular recreation area more than doubled in size throughout the day, and officials said it doesn't seem to be slowing down. Large amounts of smoke and ash were reported in Homer, but officials said the town is in no immediate danger.

A Homer Electric Association power transmission line was in the fire's path and is assumed to have been destroyed despite efforts to save it, said Kris Eriksen, a Division of Forestry spokeswoman. Retardant is being dropped on the area and utility officials will assess damage when the fire clears the area.

They said power to the line between Bradley and Soldotna had been cut off but customer service was not disrupted.

The blaze is most active along its southern edge, where it was pushing into wilderness and was no longer threatening nearby structures, Eriksen said.

"There are significantly more cabins to the north, and the fire hasn't spread that way yet," Eriksen said.

Fire crews evacuated two people by helicopter Tuesday night and saved several cabins but lost one to the fire. The lost structure was north of Deep Creek and belonged to Rob Coreson.

Eriksen said warm temperatures and low humidity in the area contributed to the fire's rapid progression since it started Tuesday evening.

"It's burning pretty good on both sides of Deep Creek Dome," she said. "The winds are picking up."

A resident Tuesday reported the human-caused fire burning about a mile southeast of her home when it was only about 100 acres.

It tripled in size in 90 minutes and within five hours the fire had reached between 800 to 1,000 acres, said Dale Anderegg, a helicopter attack foreman directing operations.

Crews have been dropping loads of retardant on the fire and using a helicopter to drop water from a nearby lake on it. Four bulldozers are also helping build fire lines.

State fire bosses called up crews from as far away as Anchorage and Fairbanks to fight the fire.