Was not an ANFO bomb - was amononia nitrate mixed with nitromethane - made it much more powerful.
It was a combination of ANNM barrels (9) and ANFO barrels (4), plus smaller amounts of other explosives.
As to their effects, read the Eglin report.
http://911blogger.com/news/2008-04-24/blast-effects-study-does-not-support-single-anfo-bomb-okc