Firefighters responded to the scene, Mike's Deli-Mart at 23221 Edmonds Way, just after 3:50 a.m. after receiving multiple reports of flames shooting from the building.
Four people who were in the apartment above the deli managed to escape thanks to some fast-acting witnesses.
"The four adults were asleep in the apartment when a stranger pounded on the door and told them to get out because the building was on fire," said Leslie Hynes with Snohomish County Fire District 1. "The residents escaped with three small dogs."
The back of the building was engulfed in flames when the first firefighters arrived from the nearby Esperance Fire Station 20. "They could smell the smoke as they left the station and there were 30-foot flames when they arrived," Hynes said.
The call went to a second alarm and it took 36 firefighters about 45 minutes to knock out the blaze.
Mike Luke, owner of Mike's Deli-Mart, said the blaze comes at a bad time economically. "Something like this really puts a kink in the business," he said.
He said he suspects an electrical problem started the fire, even though his business passed inspection just a few days ago. Investigators haven't yet determined whether that was the cause of the blaze.
The building was constructed in the 1950s.