A diplomatic protection group police officer and a 49-year-old woman have been bailed following their arrests over the Andrew Mitchell "Plebgate" affair, Scotland Yard said today.
The police constable was released from custody today after being questioned on suspicion of misconduct in a public office.
He is one of four officers to have been issued with a Regulation 15 notice, served following an alleged breach of standards of professional behaviour.
Yesterday, Scotland Yard said it expected the officer, who has been on restricted duties, would be suspended following his arrest.
But today the force was unable to comment on this matter.
The 48-year-old has been bailed to a date in August. The woman - who was questioned on suspicion of assisting an offender - was similarly released on bail to an unspecified date in August.
Their arrests came after Scotland Yard received "fresh information" relating to the investigation.
"As a result of this information and subsequent investigations, the Directorate of Professional Standards has arrested two people, a man and a woman, at two residential addresses," a spokesman said.
The Independent Police Complaints Commission, which supervises the investigation, has been informed.
Mr Mitchell quit as chief whip after it was claimed that he swore at police officers and called them "plebs" when they refused to let him leave Downing Street on his bike via the main gate in September last year.
But a subsequent Channel 4 investigation cast doubt on that account when it revealed CCTV footage which showed there was not a large group of tourists outside the main gate at the time as had originally been claimed.
An email from a civilian witness backing up the police account of events has also been called into question.
Six people have now been arrested as part of the investigation.
No decisions have yet been taken on whether anyone will be charged.
The duration and cost of the investigation has sparked anger among MPs. Operation Alice has already taken eight months and cost taxpayers more than £140,000.
Earlier this month, London Mayor Boris Johnson was forced to defend Sir Bernard Hogan-Howe's role in the case and express his "absolute confidence" in the Metropolitan Police Commissioner.