Rescue workers on Sunday searched for two people missing in the rubble of a thunderous car bomb blast blamed on the Basque separatist group ETA that shattered a nine-month-old cease-fire the group had described as permanent, officials said. Crews are using heavy machinery to remove tons of concrete and metal at the 5-story parking garage at Madrid's international airport, said Javier Ayuso, a spokesman for the Madrid city council's emergency rescue services. The garage was largely destroyed in Saturday's blast. Ayuso said it could take days to reach the spot where the van blew up. The explosion left 26 people wounded and prompted the government to halt plans for negotiations with ETA after a cease-fire that had been seen as the best chance in nearly a decade to end the nearly 40-year-old conflict in Spain's northern Basque region.