MADRID: At least four construction workers were missing after a building under renovation partly collapsed in central Madrid, authorities said on Tuesday.

The three men and one woman were reported missing by the construction company in charge, Madrid’s Deputy Mayor Inma Sanz told reporters.

“The upper floors collapsed and fell downwards, therefore we’re talking about a very significant amount of rubble that will take a long time to clear — not just hours, but probably several days,” Sanz said.

Police and firefighters were using drones and sniffer dogs to search for the missing inside the building located near the Spanish capital’s opera house and the royal palace.

Two people were lightly injured while a third person was taken to hospital with a broken leg, said Beatriz Martin, an emergency services spokesperson.