Two people died, at least 18 people were injured, and many others were trapped after an explosion rocked a four-story building in the Salamanca district in Madrid, Spain on Friday.

Two men working in the building died in the explosion, Madrid's Mayor Jose Luis Martinez-Almeida said late Friday. Of the 18 people hurt, most of the injuries were not serious, officials said.

"Some kind of works were being done in the building" in the upmarket Salamanca neighborhood where the explosion occurred, he said.

The blast emerged from a residential building just a few blocks away from the Retiro park, causing significant damage to both the building and nearby vehicles.

Firefighters continued working to control the scene and search for more possible victims. Madrid police have also deployed drones to inspect the building from above.

Individuals who were near the building at the time of the explosion said they felt other buildings also shook. Some said there was a strong odor of gas.

While authorities have not confirmed the cause of the explosion, they are looking into the possibility that it was related to a natural gas leak.

In Jan. 2021, a gas leak caused a massive explosion in central Madrid, claiming the lives of four people.