Open flames had been extinguished and only a few areas continued to emit smoke, state media reported. There was no further threat of the fire spreading.
The bodies of the dead firefighters were transported to the town of Xichang in Sichuan province, where residents presented flowers as a sign of mourning and respect. Some of the bodies could only be identified through DNA, state broadcaster CCTV reported.
Three helicopters brought in reinforcements to fully extinguish the blaze.
Changing winds Sunday apparently trapped 27 firefighters and three helpers who were battling the blaze in a remote area at an altitude of 3,800 meters (12,500 feet), according to the Ministry of Emergency Management. Despite attempts at a rescue, all 30 were confirmed dead on Monday afternoon (local time).
The Xinhua News Agency quoted firefighting official Xie Shi'en as saying wind, dry air and combustible material creative an explosive effect where the men were working.
"Among all scenarios in a fire, an explosive blaze is the most dangerous, and also very rarely seen," Xie said.
The fire advanced so quickly that trees on the ridge were consumed within seconds, surviving firefighter Wang Xin told Xinhua.
"All of a sudden, we heard a huge explosive sound from the ridge and saw a wall of flame rocket up. It was as if someone triggered a huge flamethrower," Wang said.
Most of the dead were in their 20s, although at least two were teenagers, according to state media reports. One had recently married.
China has been battling forest fires in recent weeks in various parts of the vast country, including on the outskirts of Beijing, fed by dry weather and high winds across many northern areas.
The death toll appeared to be the worst among Chinese firefighters since 2015, when an explosion at a chemical warehouse in the port of Tianjin killed 173 people, most of them firefighters and other first responders.
