A space heater sparked the fire that killed at least nine dogs Tuesday in Snohomish, officials said.
The fire broke out about 2:45 p.m. in a shop building along Lake Place, near Blackmans Lake.
A woman who lives in a two-story apartment there was working as a pet sitter, Snohomish Fire Chief Ron Simmons said. She was keeping dogs for family, friends and neighbors, he said.
Investigators believe additional dogs have died after fleeing the fire with smoke inhalation and burns. The exact count was unknown Thursday.
Pilchuck Veterinary Hospital has offered to keep the recovered remains for the owners, some of whom were out of town at the time.
The fire was ruled an accident. The property damage was estimated at $45,000.