The Chinese military on Sunday said, "abrupt change of wind direction" caused the fire to spread fast. Rescue operations and fire containment efforts are still ongoing.
PLA Daily's WeChat account earlier reported that rescuers had made contact with two survivors, before the authorities later confirmed that all those missing had been killed.
Almost 700 people were battling the fire that erupted in Sichuan's Muli county on Saturday, but contact was lost Sunday with the 30.
The bodies of the dead firefighters were brought to the town of Xichang in Sichuan province, while three helicopters had brought in reinforcements to extinguish the blaze for good.
In 2015, an explosion at a chemical warehouse in the northern port city of Tianjin killed 173 people, a lot of them firefighters and other first responders.