Sure they do. It was traced to an explosives(dynamite) theft from a mining op and the person(s) that diverted the mat'l were IDed and arrested. The 3-11 attack was a jihadi op(N African muslims) and they obtained the dynamite from the diverter(s) that worked at the mine op.
That's what I thought at first-that it was Spanish dynamite stolen from a native mine. Then I heard it was titadine, a French dynamite popular with ETA. Now, if you believe El Mundo, it was an ANFO/RDX mixture. There's also some confusion about the origins and techniques used for the timers. What can I say, except the Spaniards themselves don't seem to be that confident about the official version.