The 23-year-old striker has been an integral part of Lyon's rise to the top of the league table this season with 21 goals in 22 games, but limped out of their 2-0 with Metz on Sunday.
Having converted the latest of those goals from the penalty spot at Stade de Gerland last weekend Lacazette was forced off, with initial tests showing he had suffered a tear of the muscle in his left leg.
"Alexandre Lacazette, replaced in the 34th minute of Sunday's Ligue 1 match between Olympique Lyon and Metz, is suffering from a minor detachment of the left hamstring, without any complications," a club statement read.
"He will undergo further examinations early next week in order to set a date for his return to training."
Hubert Fournier will be without his prized asset for Sunday's trip to Monaco, and he may also miss the visit of title rivals Paris Saint-Germain on February 8 depending on the severity of the injury.
One positive for Fournier and Lyon is that Lacazette's injury may dissuade Europe's top clubs from making a bid for the forward – considered one of the hottest properties on the continent – during the January transfer window.
