Military begins work on the ground in northern port city where two explosions have left at least 55 dead. China has sent chemical experts into Tianjin to test for toxic gases after a series of deadly explosions.

The team of nuclear and chemical experts is on the ground on Friday in the northern port city of Tianjin, the scene of two massive explosions that have left at least 55 people dead.

Meanwhile, locals have expressed fears for their safety after reports there could be hundreds of tonnes of dangerous chemicals at the site.

"They say they are worried, but they believe their government said, adding that at least one person was rescued from the site on Friday morning.

The chemical experts were testing the area for toxic gases, the official news agency Xinhua said, adding that the death toll had climbed to 55, with 701 admitted to hospital.

The team of 217 nuclear and biochemical materials specialists from the Chinese military began work at the site on Thursday.

The first explosion occurred around 11:30pm on Wednesday at a warehouse in Tianjin's Binhai New Area. Only seconds later, a second blast occurred.

Rescue teams are wearing protective clothing because of fears the site is contaminated with poisonous chemicals.

According to the National Health and Family Planning Commission, 36 clinical and psychological specialists from 10 civil and military hospitals in Beijing have been despatched.