Ájtte, the Swedish mountain and Sami museum, is a popular tourist attraction in Jokkmokk. Police were called to the scene after a man and a woman entered the building and sprayed a substance into the air which forced everybody inside to flee.
A total of 20 people were affected by the spray, which police suspect may have been tear gas. Several vomited at the scene but nobody required hospital treatment.
Police suspect the spray attack may have been a coup to try and carry out a robbery at the museum. The premise hosts an assortment of precious Sami artefacts and has been adding to its collection since opening in 1989.
"We are not sure what substance was used. We are trying to get the resources to measure what it is. The police are also involved," Tomas Andersson of the emergency services told Sveriges Radio.
Since the attack on Tuesday, the museum has remained closed as the scene is being examined. The couple left the premises in the afternoon and police are appealing for witnesses in connection with the incident, in addition to a dark foreign registered vehicle which was used as the getaway car.