In March 2006, ETA declared a permanent ceasefire and expressed to join the political process. The decision may have been linked to the 2004 Madrid train bombings, which killed nearly 200 people. The attack was originally blamed on ETA, though it was soon discovered to be the work of militant Islamists linked to al-Qaeda. Like the IRA, ETA leaders may have felt that the mass casualty terrorism practiced by some radical Islamist groups discredited its violent tactics—though this is not known for certain. ETA had a secretive leadership structure.