A two-alarm fire damaged a restaurant in South San Jose on Wednesday morning.
No one was inside when flames broke out shortly before 9 a.m. at the Union Chinese Restaurant on Union Avenue, San Jose Fire Capt. Christopher Salcido said.
Firefighters believe the blaze started in the kitchen. They knocked down the fire within 20 minutes, but their work wasn't quite done.
"What does potentially happen with fires in the kitchen area and get into that flue, there is that grease build up in that flue," Salcido said. "So even when they made that initial knockdown of the fire in there, there's still some hidden fire, what they call inside that flue."
Crews spent another 20 minutes making sure the fire didn't escape from the flue.
The blaze didn't destroy the building's structure but left significant damage to the kitchen and moderate smoke damage throughout the building, Salcido said.
The cause of the fire is under investigation.
Bay City News contributed to this report.