40 Types of Dangerous chemicals detected at Blast scene in Tianjin

Officials today said that at least 40 types of dangerous chemicals were detected at the blast zone, including 800 tons of ammonium nitrate and 500 tons of potassium nitrate, the Guardian reports.
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Dangerous White Foam Rains Down In Tianjin...

By the way regarding the 500 tons of potassium nitrate. I believe this is the material Timothy McVeigh used to build a bomb that blew up the Federal Building in Oklahoma and killed and wounded an amazing amount of people.

So, it isn't hard to imagine what set off the Blast with 500 tons of Potassium Nitrate there in the first place. 500 tons of Potassium nitrate could have somehow become a bomb that put these 40 toxic chemicals literally everywhere in Tianjin and surround areas on the wind and through vehicles and through the water tables.