Good thing they swept the stadium at OU before the game, and after the explosion, with bomb-sniffing dogs...
Of course us lowly serfs in the Pajama Patrol aren't privy to the inside dope on what went bang so we gotta speculate. I just don't think it was ANFO at all. Knew a guy who used it for mining in New Mexico; they poured the stuff in drill holes as I recall then packed it with a broom handle and shot the stuff in each hole by using a quarter-stick of dynamite per hole to make it go off. Not really a high grade explosive.