A powerful explosion tore through two stories of an apartment building in Romania’s capital on Friday, killing three people and injuring at least 13 others.

Axar.az informs the explosion affected the fifth and sixth floors of the eight-story building, according to the capital’s Inspectorate for Emergency Situations.

More than a dozen emergency vehicles, including 11 fire engines and four mobile intensive care units, were dispatched to the scene of the blast on Calea Rahovei in Bucharest’s Sector 5.

The cause of the fatal blast was not immediately clear, but authorities said the gas supply had been shut off in the area as a safety precaution.

Romania’s Ministry of Health said victims had been reported with polytrauma and burns.

The ministry later said one person was found dead under a concrete slab on the building’s sixth floor. At least 13 people were transported to hospitals in the capital.