The Chinese authorities have ordered the evacuation of residents within a 3km radius of the Tianjin blast site over fears of chemical contamination.

The evacuations came after an apparent change in wind direction, and as police confirmed the highly toxic chemical sodium cyanide was found near the site.

A man was found alive 50m from the blast core, Xinhua news agency said.

At least 104 people are reported to have died in the giant blasts in the north-east Chinese port on Wednesday.