The blast, which took place in a building on Toledo Street, caused extensive damage, according to videos sent on Twitter by the Madrid City Hall’s emergency intelligence service, Emergencias Madrid.
At least four floors were damaged by the blast, and firefighters are evacuating people from the building, the service said.
“Different people are being treated (for injuries) of varying severity,” Madrid Mayor José Luis Martínez Almeida told reporters. One was sent to the hospital, he added.
Martínez-Almeida called for caution, as authorities receive even more details after the explosion. “It looks like there was a gas explosion,” he said.
Police officers are on the scene, a spokesman for the Spanish National Police told CNN.
No one was injured in a nearby nursing home and all residents were evacuated, the mayor said. The director of the Los Nogales residence, Antonio Berlanga, confirmed this account.
This is breaking news and will be updated.