They did manage to stop one of the engines after the crash, though, by smothering it with water and foam. Two engines had already stopped by themselves (damaged). The remaining one was up against the blast wall, and thet couldn't get enough water and foam in to stop it, so it ran on until the feeder tank was empty.
Presumably the engines were at idle at this point, else it would be difficult to get enough water/foam inside the engine compressors to stop it.