Unexplained incident at Swedish security services headquarters leaves eight hospitalised

The BBC initially suggested that a gas leak could be a possible cause. Yet, no excessive readings were recorded inside or around the building once surveyors arrived on-site.

Phosgene presence was indicated by sensors on the building's roof according to local media, although authorities have yet to substantiate this claim. Phosgene is primarily used in the production of plastics and pesticides and was attributed to the majority of deaths in World War I.

An exit on a nearby motorway was shut down by authorities and a security cordon implemented around the security services building. The scene's images depict police officers wearing gas masks while a helicopter hovers above the area. Instructions were given to residents in neighbouring buildings to keep their windows closed.

"Six individuals were transported to the hospital for examinations in relation to reported respiratory difficulties. Also, two of the first-response police officers have been examined," the police stated.

Residents within the cordoned-off area were prohibited from returning home. The operation concluded at 00:30 Greenwich Mean Time on Saturday. The BBC pointed out the incident's timing being concurrent with the prime minister of the country, Ulf Kristersson's, visit to Hungary – the only NATO member yet to ratify Sweden's alliance membership.

Anticipation is building for Monday when the Hungarian parliament is expected to endorse Sweden's NATO membership.