SEATTLE -- A pair of cats are being credited with waking up the residents of a Queen Anne home early Monday morning as flames moved through the attic.

"They came in, they woke us up -- they were pulling on our hair, then they went under the bed," Dennis O'Brien said as he stood on a sidewalk, watching firefighters pour water on the upper floor of his home. 

"We're fortunate to have the cats. They're both rescue cats from PAWS," he said, referring to the Lynnwood-based animal rescue organization.

The fire caught everyone by surprise, including firefighters, who had been at the home the night before to extinguish a small fire on the porch outside.

"We determined that it was spontaneous combustion," Deputy Fire Chief Angelo Duggins said of the first fire, which occurred about 11 p.m. Sunday. "He had various chemicals and things of that nature beneath the porch."

Firefighters stayed for several hours putting out hot spots and even used a thermal imaging camera to make sure there was nothing smoldering before the left.

"There was no problem that we could detect at that time," Duggins said.

At about 6:45 Monday morning, O'Brien and his neighbors were calling 911 again as smoke poured from the roof.

"By the time we arrived, it was quite a bit of smoke coming out," Duggins said. "And before we could lay our lines, there was flames coming through the roof."

Investigators are still trying to determine exactly what caused the second fire, but Duggins said it appears to have been a problem with frayed wiring near a pipe and unrelated to the fire the night before.

"The space between where the original fire was, and where the second fire was is a floor apart," he said.

Firefighters quickly got the fire under control, but Duggins said the damage to the home is extensive.

"When you're able to stand in a bedroom and look through to the sky you're talking hundreds of thousands of dollars."

He was not surprised to hear the cats were able to alert the homeowners to the smoke.

"They have a real keen sense of smell," he said.

Both cats ran under the bed after waking up O'Brien and his girlfriend, and the couple was not able to find them while they tried to get out of the house.

Firefighters found one cat after putting out the fire, and the courageous kitty is doing fine.

"We've gone through the building several times and we haven't found the other one yet," Duggins said. "Hopefully it's somewhere outside."