Two people died of carbon-dioxide poisoning at the Serbian National Library in Belgrade on Friday.

The two employees of the company in charge of maintaining fire safety systems in the building died during an inspection when the CO2 gas leaked from the system, N1 has learned.

Paramedics tried to revive the two men at the scene of the incident after firefighters searched the building and found the men unconscious, the Internal Affairs Ministry said in a press release.  

The Belgrade city fire brigade deployed five of its fire-fighting vehicles around the building with police cordoning off the area.