The area around the office was closed off while mask-wearing officers dealt with the situation
500 people in the office were evacuated by police after an 'unknown substance' was released at the headquarters in Solna, Stockholm County.
This comes as concern from foreign threats have become heightened on the buildup to the NATO decision.
Only earlier in the week, the intelligence service released a report warning of the threat posed by foreign state actors, in particular Russia, China and Iran, reminiscent of Russia's historical disdain for a growing NATO.
Comment: The Western establishment should be the first on the list of suspects, because, by this point, it makes little difference to Russia and China if Sweden joins NATO, but NATO certainly needs Sweden.
Moreover, considering Sweden's rejection of lockdowns during the contrived coronavirus crisis, evidently there are pockets of resistance to the establishment's agenda: Korybko: Russia's Avdeevka win will reverberate across Europe and accelerate geostrategic shifts
The area around the office was closed off while mask-wearing officers dealt with the situation.
Also today, Sweden's Prime Minister Ulf Kristersson met up with Hungarian Prime Minister Viktor Orban in Budapest - Hungary is the final country to vote on Sweden's membership.
Prime Minister Ulf Kristersson met up with Hungarian Prime Minister Viktor Orban in Budapest
Police said an area of 'a couple of hundred meters' around the building had been closed off after 'a potential gas leak'.
Police and emergency services were at the site and some of those taken to hospital were officers who had 'smelled an odour when they arrived'.
Around 4:30pm, police said the operation had ended.
Patrik Soderberg, chief physician at the local healthcare authority Region Stockholm said: 'Around 1pm today, there were indications that there was a dangerous substance at (the) offices.
'So far, five people have been taken to hospital with respiratory symptoms and there are also two people that have sought treatment on their own for respiratory symptoms.'
AFP reported that Sweden is currently on high alert.
It is expecting to clear the final hurdle to its bid to join NATO on Monday, with the last holdout Hungary scheduled to vote on ratifying its membership.
Comment: A warning, then?
The country has been waiting nearly two years since applying to be a member in May 2022.
Finland applied at the same time and was welcomed into NATO last April.
According to Axios, public support for NATO membership in the Nordic countries shot up virtually overnight after Russia invaded Ukraine, with a strong majority in both countries favoring joining the alliance.
It is looking highly likely that Sweden will become a member as only Hungary is left to cast their vote.
In 2022, Sweden's then Prime Minister Magdalena Andersson pointed to Russia's actions as the reason for wanting to join the defensive body.
When NATO Secretary-General Jens Stoltenberg welcomed Finland to the alliance last April, he said: 'President Putin wanted to slam NATO's door shut.
'Today we showed the world that he failed, that aggression and intimidation do not work.
'Instead of less NATO, he has achieved the opposite: more NATO. And our door remains firmly open.'
Comment: The following may not be related, but it is notable considering it also occurred in Sweden, and just a few days ago: 'Mystery sudden vomiting illness' strikes residents in Stockholm