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Spain's ruling Socialist party said Tuesday a peace process launched with a March cease-fire announcement by armed Basque separatists is now dead — not just suspended — following a weekend car bombing.

"The process is over, because this is what ETA has chosen," said senior party official Jose Blanco, naming the militant group blamed for the powerful explosion Saturday at the Madrid airport that left 26 people injured and two missing and feared dead.

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The conservative opposition Popular Party has criticized Prime Minister Jose Luis Rodriguez Zapatero vehemently for saying after the bombing that he had suspended plans to negotiate with ETA, rather than cancel them altogether.

Even after Blanco spoke, the party said the new gesture fell short. It wants a formal statement from Zapatero himself stating that he is completely ending any peace process with ETA, said Ignacio Astarloa, the party's top official for security and justice issues.

Astarloa called on Zapatero to "return to reality, with all the harshness that reality has."

The mayor of Madrid said crews sifting through thousands of tons of rubble have reached the core area of the car bombing but cannot go any faster as they search for two missing men so as not to disturb evidence for investigators.

Alberto Ruiz Gallardon told reporters at the 5-story parking garage destroyed in the blast that work is going at the fastest rate possible as the crews operate with the twin goals of finding two missing Ecuadorean men and locating the van used in the bombing, without destroying evidence along the way.

The bombing broke a nine-month cease-fire that the armed Basque group ETA had said was permanent.

ETA has not claimed responsibility for the attack, but a caller who warned authorities before the explosion said he represented the group.

Interior Minister Alfredo Perez Rubalcaba is to meet with leaders of the rest of Spain's political parties next Tuesday to discuss the attack and what it means for the now-shattered peace process.

ETA and its political supporters had complained in recent months that the process was stillborn because the government was refusing to make preliminary concessions, such as moving ETA prisoners from jails around Spain to the Basque region itself and halting police arrests and trials of ETA suspects and pro-independence politicians.

Madrid town hall has estimated that 40,000 tons of rubble will have to be removed from the bombing site at the gleaming new Terminal 4 at Madrid's airport.

The head of the city's emergency services department, Alfonso del Alamo, said Tuesday that so far 18 destroyed cars have been removed from the site and they are unrecognizable as vehicles.

The missing men are believed to have been asleep in separate cars in the parking lot when the bomb went off.