Local authorities have indicated that the deadly incident killed five individuals and injured two others. The NRK broadcaster has reported that a police officer is among the injured.
The unidentified suspect has been arrested; however, police have yet to reveal his identity or motive. Police have indicated that the suspect is a 37-year-old Danish citizen who lives in Kongsberg.
"Unfortunately, we can confirm that there are more injured and dead after the incident. The injured have been taken to hospital," police station chief Øyvind Aas in Drammen said earlier in the day.
Law enforcement officials believe the perpetrator acted alone, but referred to the incident as very "serious".
Police say it's to early to answer the question whether it was a terror attack, but that they are not ruling it out as a motive.
According to Laagendalsposten, a regional newspaper, the Norwegian Elite Police Unit, also called Delta, military forces and a large number of police cars and ambulances are in place in Kongsberg.
An investigation is underway.