The Chinese authorities have ordered the evacuation of residents within a 3km radius of the Tianjin blast site over fears of chemical contamination, reports BBC.The official Xinhua news agency said the evacuation was prompted by the threat of "toxic substances" spreading.Anti-chemical warfare troops had entered the site, it said.Eighty-five people are now known to have died and hundreds were hurt in the giant blasts in the north-eastern Chinese port on Wednesday.The operators of the Tianjin site have been accused of "clearly violating" safety rules.China has ordered officials to make nationwide checks on dangerous chemicals and explosives and to "crack down unwaveringly on illegal activities to ensure safety".