The final cleanup gets underway at the warehouse blast site in Tianjin on Friday. All of the containers, damaged vehicles and buildings at the site have been removed. Jia Chenglong / for China Daily

BEIJING, Feb - The Tianjin warehouse explosions in August that killed at least 165 people were caused by ignition of hazardous materials, improperly or illegally stored at the site.

The fire first started in a container through auto-ignition of nitro-cotton, due to vaporization of the wetting agent in hot weather. The fire spread, igniting other chemicals, including ammonium nitrate, according to a report issued on Friday by a State Council investigation team.