The 17-year-old forward enjoyed a trial at Arsenal last week and he is thought to have impressed during his time at the London club.
Boss Arsene Wenger has held a long-term interest in the 17-year-old and has now firmed up his interest with a bid.
Caen are resigned to losing Niang following their relegation from Ligue 1 and a host of clubs have expressed an interest in signing the teenager.
Arsenal are hoping to tie up a deal with Caen before Man City can get a firm bid in.
Source: Skysports
Source: DSG
