About 140 firefighters rushed to the scene early Saturday afternoon and extinguished the fire in just over an hour, the Los Angeles Fire Department said.
The two critically injured men have severe burns and the third was transported in fair condition with unspecified injuries, officials said. The three were taken to hospitals.
The one-story building, which sits along a row of commercial businesses, suffered serious damage.
“The well-coordinated LAFD defensive operations prevented either of two adjacent businesses from sustaining fire damage,” the department said.