An explosion at an eight-storey apartment building in Bucharest collapsed several floors, killing three people and injuring 13, Romanian authorities stated on Friday.

"So far, 13 victims have been transported to the hospital, one refused transport, and three other people have died," the official Emergency Department Facebook account said in a statement. "The third victim identified was trapped under the rubble, namely under a concrete floor on the 6th floor. She is not showing any vital signs."

The blast broke windows at a nearby high school, news website Hotnews.ro reported. It also completely collapsed two floors and affected others below, local media said.

At least two died and 12 were injured, news website Biziday.ro cited emergency services and the health ministry as saying. Teams were searching the blast site for others trapped, Biziday said.

This is a developing story.