More than 200 nuclear and chemical experts are testing the site of a series of explosions in China for toxic gases.
At least 50 people were killed and hundreds injured when explosives at a warehouse detonated on Wednesday - creating a blast which could be seen from space.
Environmental campaigners are worried substances from the site - in the city of Tianjin (pron: te-an-jin) - could be dangerous.
Dan Agio witnessed the explosions:
