Columns of smoke from fires still burning on Friday rose from the blast site amid the devastation of crumpled shipping containers, thousands of torched cars and port buildings reduced to burnt-out shells. Rescuers pulled one survivor, from the wreckage, a city official told reporters. State television later said it was a firefighter.

The municipal government in Tianjin, a key port and petrochemical processing hub about 75 miles east of Beijing, said 701 people were injured, including 71 in serious condition. It gave no figure for the missing.

Tianjin is the 10th largest port in the world by container volume, according to the World Shipping Council, and the seventh-biggest in China. It handles vast amounts of metal ore, coal, steel, cars and crude oil.

Ships carrying oil and “hazardous products” were barred from the port Thursday, the Tianjin Maritime Safety Administration said on its official microblog. It also said vessels were not allowed to enter the central port zone, which is near the blast site.

State media said senior management of the company had been detained, and that President Xi Jinping demanded severe punishment for anyone found responsible for the explosions.

“It was like what we were told a nuclear bomb would be like,” said truck driver Zhao Zhencheng, who spent the night in the cab of his truck after the blasts. “I've never even thought I'd see such a thing. It was terrifying, but also beautiful.”

In a sign of sensitivity over the hazardous materials stored at the warehouse, state broadcaster CCTV went into a live broadcast of a news conference in Tianjin when the head of the municipality's Environmental Protection Bureau chief, Wen Wurui, was speaking. He said there had been no apparent impact on air monitoring stations, but that water samples were still being examined.

However, when a reporter asked him whether the chemicals at the warehouse had been stored far enough away from residences in the area and Wen seemed at a loss for a response, the broadcaster suddenly cut away from the news conference, only to return to it again later.

Authorities said the blasts started at shipping containers at the warehouse owned by Ruihai Logistics, a company that says it stores hazardous materials including flammable petrochemicals, sodium cyanide and toluene diisocyanate.

The initial blast apparently triggered an even bigger one. The National Earthquake Bureau said the first blast was the equivalent of 3 tons of TNT, and the second 21 tons. The enormous fireballs from the blasts rolled through a nearby parking lot, turning a fleet of 1,000 new cars into scorched metal husks.

As is customary during disasters, Chinese authorities tried to keep a tight control over information. Police kept journalists and bystanders away with a cordon about a mile from the site. On China's popular microblogging platform of Weibo, some users complained that their posts about the blasts were deleted, and the number of searchable posts on the disaster fluctuated, in a sign that authorities were manipulating or placing limits on the number of posts.

The Tianjin government said that because of the blasts it had suspended online access to public corporate records. These records might be used to trace the ownership of Ruihai. It was not clear whether the blackout was due to technical damage related to the explosion. No one answered the phone at the Tianjin Market and Quality Supervision Administration or the Tianjin Administration for Industry and Commerce on Thursday.

Ruihai Logistics said on its website — before it was shut down — that it was established in 2011 and is an approved company for handling hazardous materials. It said it handles 1 million tons of cargo annually.

Photos taken by bystanders and circulating on microblogs show a gigantic fireball high in the sky with a mushroom cloud. Other photos on state media outlets showed a sea of fire that painted the night sky bright orange, with tall plumes of smoke.

About a mile from the explosion site is the luxurious Fifth Avenue apartment complex on a road strewn with broken glass and pieces of charred metal thrown from the explosion. Like surrounding buildings, the Mediterranean-style complex had all its windows blown out, and some of its surfaces were scorched.

“It's lucky no one had moved in,” said a worker on the site, Liu Junwei, 29. “But for us it's a total loss. Two years of hard work down the drain.”

“It had been all quiet, then the sky just lit up brighter than day and it looked like a fireworks show,” said another worker on the site who gave just his surname, Li.

Al Jazeera and The Associated Press