At least three people died and six were injured on Wednesday when a building in central Madrid belonging to the Catholic Church was blown apart by an explosion, local authorities said.
Initial investigations suggested that the blast in Calle Toledo, a street leading out from the city center, was caused by a gas leak, Mayor Jose Luis Martinez-Almeida said.
"The most likely hypothesis is a gas leak, there was a person working on the boiler," the mayor told reporters as he announced that a body had been discovered under the rubble, raising the death toll to three.
"Firefighters still have to retrieve the corpse," he said, without providing further details.
Earlier, a Church official said one church volunteer was missing. One of the casualties was an 85-year-old woman, authorities said.
Two of the injured were transferred to hospital, one in serious condition with a head injury.
Smoke billowed out of the partly collapsed building and rescue workers evacuated elderly people from a nearby nursing home.
The top five floors were totally destroyed, with walls blown out, while the bottom two floors were still mostly intact, but charred in places from the flames.
The building was a complex that provided residential training for priests and also gave meals to homeless people, a neighbor said.