RENO, NV - Three people escaped a house fire within seconds thanks to a smoke alarm, but their pets weren't so lucky.

It all happened Monday afternoon, on the second floor of an apartment house, located on 600 block of Lake St in downtown Reno. The fire heavily damaged one building and burned another.

Shivering in the cold, Anita Brown looked on toward the smoldering ruins. Her apartment was gone with everything this owned inside it. "It's just stuff ... I'm worried about my cats," she said, referring to her two 15-year-old cats who lived in the apartment. According to Battalion Chief Jeff Frank, at least 4 cats died in the blaze, two believed to be hers, two others strays she was feeding.

Fire investigators say it started with a candle setting fire to some bedding. It may have smoldered for some time before suddenly bursting into flame.

Eyewitness Ed Saulnier said he was walking by when he first noticed the smoke and then, "just poof, a big ball of fire just exploded out of the building.'"

The speed of the fire may have been aided by the home's century old construction. Built in 1905, it lacked modern construction features that tend to slow a fire.

The building, which is located at 644 Lake St, started on fire at about 12:40pm Monday. The house next door, 636 Lake St, began to catch fire but firefighters were able to prevent its spread.

All occupants of the apartment were able to get out of the house safely. Firemen say a smoke detector gave one first floor occupant the time needed to exit.

One firefighter was injured by steam burns through his gloves whlie searching the upper floor for possible victims. No one else was injured.