Leicester won 25-21 in a heated European Rugby Champions Cup group match on Sunday.
Toulon said on its website on Wednesday that it decided to open an investigation after Leicester complained about the behaviour of prop Martin Castrogiovanni and fullback Delon Armitage.
Castrogiovanni, a former Leicester player, allegedly used "insulting terms" toward Leicester sporting director Richard Cockerill, as Cockerill was giving a post-match news conference, while Armitage is also alleged to have insulted spectators at Welford Road.
Toulon says it "will punish the players if deemed necessary," and "takes the opportunity to offer its apologies to Leicester Tigers for the inconvenience caused."Suggest a correction