Now, a preliminary investigation has been opened to see whether this is a health and safety offense leading to bodily harm, reports news agency TT.
The smoke sent a total of 27 people to the hospital, writes news agency TT, though all were with reportedly non-life-threatening injuries, according to Mikael Grumstedt, acting medical chief at Kiruna's hospital.
One patient was transferred by helicopter while most of the others were hospitalized for observation, he said. A few have even been released.
LKAB spokeswoman Johanna Fogman told Swedish Radio's Sami language program earlier in the day that all workers in the mine were accounted for and that there was no indication that anyone was said to be injured by the smoke.
News agency TT reported that a truck caught fire about 8:30 a.m. more than a kilometer underground in the LKAB mine in Kiruna. Firefighters were able to put out the flames and pump out the smoke.