Spanish Police say three people were injured in the partial collapse of a building in central Madrid on Tuesday adding that none of the injured was in a serious condition.

At least four construction workers remain unaacounted for 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.

The partial collapse of the five-storey building occurred inside, leaving its facade intact, Martin added. 

The city's emergency services had said they treated and discharged three workers at the site of the incident but also said an unknown number of workers were missing in a post on X. 

They  also cordoned off an area in Madrid near the Opera house after the building collapsed to search both within and outside the building for the missing persons. 

In a post on X, the emergency services said that the local police was at the scene and had deployed drones, possibly for search and rescue efforts. 

"The civil protection agency had also been deployed" it said in the post

"It's full of ambulances and police, and they won't let us in." an eyewitness told the Spanish newspaper El Pais just after the incident occured on Tuesday afternoon. 

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