Operation Alice officers were tasked with investigating who passed information to The Sun and The Telegraph newspaper regarding the "Plebgate" incident, including whether the leak came from within the police force or from a third party.
They examined a police witness statement from the incident and investigated if there was a conspiracy between the officer and another party.
They also investigated claims made by Andrew Mitchell that police lied in the police log of the incident.
I've just got off the phone to Andrew Mitchell, the MP accused of calling police officers in Downing Street plebs - which he's always denied.
He told me he was informed by the IPCC yesterday that police files into what happened were about to be handed over to the CPS. He was also contacted earlier today by the police officer in charge to say it was about to happen.
Andrew Mitchell has told ITV News Central he is pleased at the progress being made in the so called 'Plebgate' investigation.
The Metropolitan police has tonight handed a dossier of evidence to the Crown Prosecution Service.
It follows an incident at the gates of Downing Street last September when the Sutton Coldfield MP was asked to get off his bike and use a side exit. Police officers claim the MP called them "plebs" - an allegation vehemently denied by Mr Mitchell.
Mr Mitchell told ITV News Central he took a call from the Deputy Commissioner of the Metropolitan police about the latest developments as he was attending an event in his constituency. He said he has always maintained he was "fitted up" by the police in an effort to toxify the tories.
Scotland Yard officers carried out inquiries as part of Operation Alice, the investigation in connection with an incident involving then Cabinet minister Andrew Mitchell in Downing Street.
A copy of the file handed to the Crown Prosecution Service was also given to the Independent Police Complaints Commission, which is supervising the investigation.
The incident in September last year became popularly known as "Plebgate" following claims, denied by Mr Mitchell, that the MP called officers "plebs" in a dispute.
Scotland Yard has passed a file of evidence linked to the "Plebgate" scandal to the Crown Prosecution Service, the force has said.
At least 10 police officers are suspected of being involved in an alleged plot to discredit ex-cabinet minister Andrew Mitchell, who was accused of calling Downing Street armed guards “plebs”, according to a report by the Sunday Times (£).
The Independent Police Complaints Commission (IPCC) has expanded its part in the criminal investigation into the incident after receiving new information.
The female police officer who was arrested over alleged media leaks about the "plebgate" affair was present at Downing Street during the time of the incident in September, the Metropolitan Police said.
A 46-year-old female police officer from Scotland Yard's Diplomatic Protection Group was arrested over alleged leaks to the media linked to the Andrew Mitchell "plebgate" affair, the Metropolitan Police said.
A 46-year-old male officer arrested yesterday has been bailed to return on a date in March.
MPs say the police watchdog, the IPCC, should be investigating the "plebgate" affair, which involves former Gedling MP Andrew Mitchell.
Mr Mitchell quit his cabinet post as chief whip following a row over claims he called police officers "plebs".
MP for Leicester East, Keith Vaz, who chairs the Home Affairs Select Committee, says the case shouldn't have been referred to another police force to investigate.
David Cameron said it was "very important" the investigation into the 'plebgate' affair was "thoroughly carried out and proper answers are delivered".