The headquarters of the Swedish Security Service in Stockholm was evacuated on Friday, with several people taken to hospital after a possible gas leak.
A perimeter of 100 m around the headquarters was cordoned off and a "handful" of people were taken to hospital, some of whom were police, after detecting an odour at the scene, according to the police web page.
Police later said the cordon had been lifted.
Minister of Justice Gunnar Strommer told TT news agency that the government was following the situation and in contact with the Security Services.
Earlier on Friday, Swedish Prime Minister Ulf Kristersson held a joint news conference with Hungarian counterpart Viktor Orban as the Hungarian parliament is set to ratify Sweden's NATO application next week - the only remaining hurdle before Sweden can become member of the military alliance.