Copenhagen - Denmark captain and Brondby defender Daniel Agger is to be investigated by the country's FA after allegedly elbowing FC Copenhagen's Mattias Jorgensen in a hotly-contested derby on Monday.
The incident in the goalless draw was not seen by match officials.
"The disciplinary authorities have asked Brondby for an explanation of the episode, before making a decision if the offense documented by television images is punishable or not," the DBU said in a statement.
FC Copenhagen are second in Denmark's Superligaen on 43 points, 11 behing leaders FC Midtjylland, with Brondby in fourth on 35.