A gas explosion killed three people, leaving the other four injured, in the southern city of Bytom in Poland on Saturday.

The explosion which occurred at around 1 p.m. local time on the ground floor of a building in the city center of Bytom, caused the death of a 39-year-old woman and her two daughters, who are five and seven years old respectively, according to the Polish News Agency.

Three of the injured were also residents of the same tenement building, while the fourth one was a woman who was just walking nearby at the time of the explosion. The woman was badly hurt and transported to a local hospital immediately by helicopter.

Firefighters sent to the scene put out the fire caused by the explosion and searched thoroughly, then confirmed that there was no more victims.

An inspection will be launched by the authorities to determine the cause of the deadly explosion.