Sarajevo  - Bosnian police have detained four people on suspicion of unintentionally causing a gas explosion at an apartment building in the downtown Sarajevo in which one person was killed and three badly injured late Sunday, Bosnian media reported Tuesday.

Those detained late Monday included the director, technical expert and workers of Viner Projekt, a company that had been testing terrain in front of the building where the explosion occurred. They had reportedly punctured a gas line.

The explosion caused a fire on the top floor of the four-storey building in the city centre, completely destroying three apartments and shattering windows in surrounding buildings and nearby cars.

Three people were in a critical condition, Sarajevo clinic hospital spokesman Biljana Jandric said. (dpa)