Sanchez was supposed to resume training on Sunday but his resumption was postponed due to his illness.
Sanchez who reportedly wants a move away from Arsenal was given an extended break following his participation in the FIFA Confederation Cup with Chile.
Although he was supposed to resume training on Sunday, July 30, the 28-year-old called in sick sparking further reports of his determination to leave the club.
Arsene Wenger had however calmed fears of Arsenal fans by revealing that the striker would instead resume on Tuesday.
Arsenal Twitter handle shared a photo of Sanchez in training with the caption; “Look who's back in training.”
Sanchez reportedly wants a move to Manchester City so he can compete in the Champions League.
Wenger has had to shut down reports of his star player’s exit all summer, insisting that the forward will be at the club next season.
Sanchez has just a year left on his Arsenal contract and has so far turned down all offers for an extension.