According to German tabloid Bild, the Bayern Munich duo were invovled in a fist-fight during training on Thursday.
Lewandowski reportedly scolded the French winger at a behind-closed-doors training session, resulting in an argument which eventually escalated into a full on fight with both players landing reported punches to the face.
Niklas Suele and Jerome Boateng separated the two attackers who will undoubtedly face repercussions for their behaviour.
Bayern moved top of the Bundesliga standings with a 5-0 thumping of rivals Borussia Dortmund last weekend.
The league holders next face Fortuna Dusseldorf on Sunday and head coach Niko Kovac will be hoping that the incident doesn't have a negative outcome on his troops performance, as they aim to hold onto their narrow lead at the top.