MADRID — A powerful gas explosion tore through a residential building in central Madrid on Wednesday, killing four people and ripping the facade off the structure.

A tower of smoke rose from the building, where repairs were being done to a gas boiler, and billowed through Toledo Street, near the city’s center. Aerial footage shared by Spain’s National Police showed rubble covering a nearby schoolyard — though Madrid’s mayor said no one was seriously injured at the school.

All students and staff were inside the school buildings at the time of the blast.

At least 11 people were injured in the explosion, one seriously, the Madrid emergency service said in a tweet.

The Spanish government’s representative for the Madrid region, José Manuel Franco, confirmed three casualties and the Catholic parish that owned the damaged building said the fourth victim was an electrician, a father of four, who was working on the boiler and had initially been considered missing.

A police spokesman on the ground told reporters that firefighters were trying to put out a small fire inside the building before they could bring in dogs, rescue teams, and experts to assess the structure of the damaged premises.

An Associated Press reporter saw emergency workers carry two bodies away from the area, one that firefighters covered with a blue blanket and another shrouded in reflective emergency sheeting.

The building belongs to the nearby La Paloma Catholic Parish and hosted the offices and apartments for some of its priests, Madrid Archbishop Carlos Osoro told Spanish public broadcaster, TVE. He confirmed that none of the clerics were among the victims.

Emy Lee Grau, a local resident who was watching television in a building across the street, said that the moment of the blast was “terrifying.”

“Everything shook, it felt like the roof was falling on us. We were terrified when we saw the amount of smoke coming out of the church’s building,” the 20-year-old Madrid resident told The Associated Press.

A nearby nursing home was evacuated and no injuries were initially reported among the 55 residents, Madrid Mayor José Luis Martínez Almeida told reporters. They were taken to a hotel across the street and were later sent to other care homes, officials said.

Martínez Almeida also said that some mild damage had been identified in the school, where he said people suffered no more than “scratches.”

Neighborhood resident Leire Reparaz said she heard the explosion and wasn’t immediately sure where it was coming from.

“We all thought it was from the school. We went up the stairs to the top of our building and we could see the structure of the building and lots of gray smoke,” the 24-year-old said.

Associated Press photographer Paul White contributed to this report.