Explaining that the alleged “serious incident” happened on Saturday 9 October, Police said last week that they were urgently looking for several people who were around the area of the Trafalgar Pub that evening.
They have since managed to track down the possible witnesses, who are now helping with their investigation.
The officer, who was not on duty at the time of the alleged sexual offence, was arrested at a private address on Friday morning and held in police custody.
On Saturday afternoon, Police confirmed that he had been released on bail.
Last night, they confirmed that the officer will not be returning to work while the investigation remains ongoing. They said he had been suspended from duty in what was described as a “usual internal measure.”