The match had been underway for just over 17 minutes when it was interrupted, and a moment later the players were sent to the locker rooms.
One person was taken by an air ambulance and, according to TV4, was conscious.
The match resumed after about a 15-minute break, and Västerås took the upper hand thanks to Philip Bonde, who headed in both goals.
Oliver Berg scored for BP, but he was also unfortunate when he missed a weakly struck penalty with 15 minutes left, which Västerås goalkeeper Elis Jäger was able to save.
