Not exactly. It was a combination of ammonium nitrate fertilizer and fuel oil (y’know, the stuff that you use to heat your house with in large swaths of New England; the deceased boiler in my basement ran on fuel oil). That combination is called ANFO. But, by itself, it’s quite stable; you need an explosive to set it off. Most of the time, that would be a detonator, but I don’t know what McVeigh and Nichols used as the detonator. I believe that whatever they used as a detonator was set off remotely, by radio.