The French defender has been sidelined with an achilles injury, which is the reason the club says he will return to England, but there are genuine concerns regarding his overall behaviour.
Sakho reportedly arrived late for the squad's flight to America and also interrupted an interview with manager Jurgen Klopp at Alcatraz prison in San Francisco.
Question marks have been raised about Sakho's attitude during the summer camp thus far and he will head back to Melwood to undergo rehabilitation on his injury.
The Anfield club have not commented on the situation or indicated if the 26-year-old would be punished.
Two other injured players, Joe Gomez and Lucas Leiva, have stayed on with the playing group who are preparing for International Champions Cup fixtures with Chelsea and AC Milan in California and a friendly with AS Roma.