In the middle of the first half, the former Barcelona striker apparently delivered an unprovoked blow to Jon Jönsson’s stomach, sending the Elfsborg player to the ground.
The referee missed the incident and Larsson stayed on the pitch to head in Helsingborgs’ second goal.
The incident overshadowed a thriller of a game, which Helsingborgs eventually won on penalties after the teams finished extra time level at 4-4.
A ‘private person’ reported the punch to the police, and the suspected assault will now be investigated.
“Wherever it happens, it is very important that nobody should have to be exposed to violence in society without it being tried in court,” said prosecutor Sven-Erik Alhem to Dagens Nyheter.
“Punching is not part of the rough and tumble you can expect as a football player,” said Alhem.
After the match Larsson said that he was simply trying to shake himself free from Jönsson, who was holding him.
The matter has been blown out of all proportion, according to Helsingborgs sports director Bosse Nilsson.
“It’s like shooting mosquitoes with a canon,” he said to Expressen.