A firefighter was pulled alive Friday from the rubble of catastrophic detonation in a Chinese port, after at least 17 of his colleagues were killed in the disaster.

Zhou Ti, 19, was being treated for chest injuries at a hospital in Tianjin and was in stable condition, the city government said on a verified account on China's Twitter-like Sina Weibo.

Images showed attached to the posting showed Zhou lying on a hospital bed, his eyes closed, reddish splotches covering most of his face and a net bandage on his head.

The young man was one of more than 1,000 firefighters sent to a burning hazardous goods storage facility at the northern port.

The enormous blasts that followed Wednesday killed at least 50 people and injured 701, according to official media, and more firemen were still missing.

PHOTO: Explosion rocks China's Tianjin

Officials said Zhou had no recollection of when he reached the scene, and it was not clear whether he was among the first responders to the site who were caught up in the giant blasts, or if he arrived some time later.

The firefighters initially sent to the scene were "investigating and testing" the area and their reinforcement were arriving when the first blast hit "all of a sudden", Zhou Tian, head of the Tianjin firefighting bureau, told a briefing Friday.

"The firefighters were at the centre of the explosion and were unprepared," he added.

Commentators on social media condemned the handling of the blaze and the toll among emergency responders.

"Why let young firefighters who have no experience go to the scene?" asked one Weibo poster.

Others questioned reporting in China's state-controlled media, and the stress on rescue efforts when disaster strikes.

"Every time when disaster happens, state media always spread heroic acts," the poster wrote. "In the end, people are touched by these stories. Then nobody asks the cause of the accident to explore the truth."

The Southern Weekly newspaper, which sometimes takes a more independent stance, quoted a fireman on its website Thursday saying that fire crews hosed water at the blaze for more than 10 minutes before the blast.

No one warned them of the risk that there could be dangerous chemicals that would react violently with water, said the report, which was later taken down from the website.