Four people were injured in an explosion that ripped through a residential building in Istanbul’s Üsküdar district, according to initial reports Monday.

Unconfirmed reports say the blast at a four-story building stemmed from a natural gas leak. Footage from the scene showed an entire wall of the building collapsed while media outlets reported that the blast, on the third floor, shook nearby buildings in the narrow alley.

Firefighters and paramedics were deployed to the scene and are searching through the rubble.

Murat Sefa Demiryürek, district governor of Üsküdar on the city's Asian side, said two of the injured sustained major wounds. Quoted by Demirören News Agency (DHA), Demiryürek said they evacuated two neighboring buildings due to extensive damage. He added that an investigation was underway to find the cause of the explosion.

District Mayor Hilmi Türkmen told DHA that the explosion was "frightening" and felt in a large area. "It is a central neighborhood and we heard a very loud blast," he said. Türkmen said one of the injured was a person who "fell off the from the fourth floor" due to the impact of the blast. He said they coordinated the evacuation, and the electricity along with the natural gas across the street was cut off as a precaution.