Six people are in critical condition, twelve are seriously injured and six are slightly injured, local media reported. Seven people were treated on the spot and were able to go home.
The explosion occurred around 3 a.m. on the night from Saturday to Sunday. It is not known how many people were in the building at the time. It is likely that there were more casualties. The fire that started after the explosion has now been extinguished, but there are almost certainly people still under the rubble.
The rescue operation is still in progress.
The gas company Azerigaz has since issued a statement that a gas pipe may have leaked and that that led to the disaster. A number of apartments are also located in the building in which the nightclub was located. There was little left of that either.