Scotland Yard said on Thursday that because of "ongoing developments", no interim report had yet been submitted to the Crown Prosecution Service.
Investigators have taken statements from all 800 officers in the Diplomatic Protection Group (DPG) as part of the inquiry.
Two other men have been arrested so far. A 52-year-old Pc who is also from the DPG was held on suspicion of misconduct in public office and bailed until a date in February. A 23-year-old was arrested on suspicion of intentionally encouraging or assisting the commission of an indictable offence and also released on bail.
Four other constables in the unit, which is responsible for protecting Government officials and diplomats, have been placed on restricted duty over misconduct claims.