They say it was around 2.7k tons of ammonium nitrate (confiscated 6 years ago) and that 2.4 kg is equivalent to 1kg of TNT. So they roughly put this at 1.1k to 1.2k tons of TNT and the previous first and second biggest non-nuclear explosions were 3k tons and 500 tons.
To put this in perspective Hiroshima was 15k tons of TNT.
The Oklahoma guy from a long time ago had the same stuff but only had 2 tons of it.
Nasty stuff.