The number of people killed in giant explosions in the Chinese port of Tianjin has risen to 85, officials said Saturday.

At a press conference the northern city's deputy propaganda chief said 21 firefighters were among the dead after the enormous blasts at a hazardous materials storage facility.

Hundreds of people were also injured in the disaster, which has raised fears of toxic contamination after officials said they were unable to identify what chemicals were at the site at the time.

Questions have also been raised over whether firefighters responding to an initial blaze at the warehouse could have contributed to the detonations by spraying water over dangerous substances.

A team of 217 nuclear and biochemical materials specialists from the Chinese military was deployed to the site in the aftermath of the blasts.

But experts have said toxic gas indicators were within normal ranges and the air "should be safe for residents to breathe".