More than 1,000 firefighters and nearly 200 fire engines had participated in the rescue as of 9 am on Friday following the massive blasts that happened in Tianjin on Wednesday night, Zhou Tian, chief for firefighting at Tianjin's public security bureau, said.

Rescuers pulled alive a survivor on Friday morning. The survivor is a 19-year-old firefighter and is in hospital for treatment, according to the government of Tianjin's Binhai New Area, where the accident happened.

The blasts had left 55 people dead as of Friday morning, according to China Central Television.

Hospitals in Tianjin received 701 people injured as of Friday morning, including 70 in critical conditions, Wang Jiancun, chief of Tianjin's health bureau, said.

The rescuers are facing a risky environment as there are many unknown chemicals left at the site of the devastation and may explode without warning, Zhou said.

"Slight explosions have occurred many times during the rescuing operation, which have posed life threat to the rescuers," Zhou said.

The rescuers have taken many measures to minimize risks such as burying chemicals with dry sand, he said.

Zhou said the first group firefighters arrived at the site on Wednesday night after they received reports of fire, and an explosion occurred upon the arrival of the second group of firefighters.

As of Thursday night 17 firefighters died in the accident, and an unknown number of firefighters were missing.