BEIJING (AFP) - Cyanide levels more than 350 times standard limits have been detected in water close to the site of deadly explosions in the Chinese port city of Tianjin, officials said on Thursday.

The Tianjin environmental protection bureau said the chemical was detected at 25 water monitoring sites within the cordoned-off area around the blast site on Wednesday.

"An excessive level of cyanide was detected in eight locations with the highest reaching 356 times" the permitted level, the bureau said.