Among the missing are 85 firefighters, Xinhua said, citing local officials. A total of 46 people have been rescued from the site, the latest a man in his 50s found 50 meters (164 feet) away from a “burst point,” Xinhua reported. He suffered a respiratory tract burn and was in stable condition, the news agency cited Li Jingmei, a Tianjin doctor, as saying.

Saving lives will remain the top priority even beyond the 72-hour golden period for rescue, Minister of Public Security Guo Shengkun said, according to Xinhua.

Earlier Saturday people were evacuated from a 2-mile zone around the industrial site on contamination fears as the investigators try to confirm media reports that chemicals stored in the warehouse may include as much as 700 tonnes of sodium cyanide. China sent a team of nuclear and biochemical emergency military workers to the area east of Beijing to search for survivors, the Ministry of National Defense said.

Exposed Weaknesses

The deadly explosions at a storage site for hazardous materials exposed weaknesses in how chemicals are transported and stored in China, prompting the State Council Work Safety Commission to order nationwide inspections. Local governments have until Sept. 15 to report back. Tianjin, the world’s 10th- busiest port, has become a gateway to northern China for shipments of metal ore, coal, autos and crude oil.

President Xi Jinping on Saturday urged authorities to learn from the “extremely profound’ lessons in the latest incident.

Xi said in a statement that the Tianjin blasts and a string of serious accidents recently exposed severe problems in the work safety sector, and that authorities must always focus ‘‘safe growth’’ and keeping in mind ‘‘people’s interests first.’’

Preliminary investigations show toxic chemicals including sodium cyanide may have been stored at the warehouse, Gao Huaiyou, deputy director of the Tianjin Administration of Work Safety.

Hazardous Pollutants

People from nearby shelters around the warehouse district were evacuated about 10:50 a.m. Saturday because a change in wind direction could disperse hazardous pollutants, state-run Xinhua reported. Volunteers told people to wear long-sleeved clothes and masks and to leave in an orderly fashion, the news agency said.

The air Friday evening fell below the ‘‘safe standard,’’ forcing rescuers to temporarily leave the vicinity, Xinhua reported. The State Oceanic Administration has tried to soothe public concerns over pollution by saying no hazardous chemicals were detected in waters off the blast site.

The death toll included at least 21 firefighters, the highest for a single rescue mission since the People’s Republic of China was founded in 1949, Xinhua said. The blasts also left 722 people hospitalized, including 58 in critical or serious conditions.

Officials acknowledged that first responders did not know what was on fire and used water to put out flames, which then caused more explosions, according to Xinhua.

More than 1,000 firefighters, including hundreds from neighboring Hebei province, remain on the scene, said Zhou Tian, the municipal firefighting bureau chief.

Executives of Tianjin Dongjiang Port Rui Hai International Logistics Co., the operator of the location of the explosions, are in police custody, Xinhua said Thursday. Shipping and logistics operations at the port were still disrupted Friday.

Tianjin is home to manufacturing operations for companies including Deere & Co., which said it temporarily suspended operations in the northeastern city.