OK.
Here's a paragraph from a "FAZ" report. They seem to be more agressive than "Spiegel". "FAZ" is saying they are directly involved in planning the attack. I translated what I felt was the pertinent paragraph.
The, or those, one(s) arrested have been known for some time to be islamic extremists and potential assassins, according to television reports. They have been directly involved in the planning of the March 11th attacks. They have had connections to radical Islamic Hamas and other extremist groups. The clues don't lead just to Hesse, but to other German states as well, according to the television reports.
The terrorism expert Udo Ulfkotte said in n-tv that a Syrian and persons of other nationalities, who lived in Hesse, are also involved in the matter. The operation against them is forthcoming.
"FAZ"....Spur der Madrider Anschläge führt nach Deutschland
Ironically, the "FAZ" link you posted leads to a page where all the articles are peeing and moaning about the US's veto of the UN resolution condemning Israel's attack on Yassin. Yet the article about the Madrid bombing says the terrorist suspects who lived in germany had connections to Hamas.
Sooner or later one has to hope these people can connect the dots.
longjack