At least 17 people were killed and another 400 were injured, including 32 critically, after a series of blasts at the warehouses in the port of Tianjin late on Wednesday, which sent waves of explosions that shattered nearby vehicles, roads and buildings.

The first explosion at a warehouse of chemical materials came at around 11:20 pm on Wednesday, followed by a number of blasts later on. The explosions also extensively damaged nearby infrastructure, the new office of the Tianjin Binhai New Area said on its official blog.

Nineteen firefighters were trying to extinguish the fire and search for survivors at the initial blast site, and at least six firefighters have been killed, the Beijing News reported. Seven to eight fire engines also were destroyed, the report said.

The firefighters still have to work carefully to prevent secondary blasts, and the nature of the blast material, including batteries, means the firefighters can only use sands to extinguish the fire.

In addition to the batteries, the warehouses also piled flammable materials including oxidants, potassium and sodium, the report said.

Hundreds of injured were taken to hospitals in Binhai new district, and many have been transferred to hospitals elsewhere. The Teda Hospital, the closest one to the explosion site, was full of injured, and Tianjin Port Hospital has received more than 300 people hurt in the blasts as of 1 am on Thursday, according to the Beijing News.

The China Earthquake Networks Center said that the strongest blast took place 30 seconds after the first blast, and it was so powerful that it registered at a nearby earthquake monitoring center. The center said the intensity of the blast was equal to 21 metric tons of TNT.

In an instruction, Chinese President Xi Jinping called for every effort to search for the missing and contain the fire.

Premier Li Keqiang also urged authorities to intensify search and rescue. He asked the injured to be treated properly to minimize death from injuries. Li also vowed a thorough investigation of the accident and to ensure open and transparent disclosure of information to the public.

Images and videos on social media late early on Thursday showed that huge fireballs were sent into the sky; vehicle windows were shattered; and apartment doors were ripped off from blast reverberations.

The State Council has sent a special work group, led by State Councilor and Minister of Public Security Guo Shengkun to the blast site.

The warehouse where the blast first occurred is owned by the Tianjin Ruihai International Logistics Co, and company executives have been taken into custody, according to the news office of Binhai New Area.

CCTV reported that the air-quality monitoring stations have not monitored a rise in pollutants caused by the blasts.

Satellite map shows a residential community with 5,617 households only 700 meters away from the blast site. The blasts also destroyed offices of five or six logistic companies.

The explosions also disrupted traffic in the city early on Thursday, as authorities were forced to close a new urban transit line and several road entries to the Tianjin port. A highway inside the city also was closed, the Binhai New Area said.

The National Health and Family Planning Commission said in a statement that it has sent special groups of medical experts to Tianjian to aid the medical effort.

The country's top health authority is busy with providing a medical response to the blasts, which occurred at a warehouse in the north China port city of Tianjin on Wednesday night.

So far, the explosions have killed 17 people and injured hundreds as of Thursday morning, according to rescuers.

Medics specializing in blast injury and burns from Beijing are treating the injured in Taijin. The commission is also collecting drugs and medical appliances to be sent to Tianjin for disaster relief.

Contact the writers at xuwei@chinadaily.com.cn