Officers are appealing for information after the sex attack which happened between midnight and 12.30am on Sunday in the toilets at Mature Club & Cocktail Bar on The Parade, Wellington.
Detective Inspector Jo Whitehead, said: "We believe there were a number of people in and around the club toilets at this time. If you were there we’d urge you to come forward, no matter how insignificant you feel your information could be.
"We understand this incident will be very worrying to the local community and I want to reassure the public that we are doing all we can to apprehend the suspect.
"Earlier, this morning officers carried out warrants in relation to our investigation at properties in Vineyard Road, in Wellington, and Bailey Road in Arleston.
“As the warrants were carried out there may have been some disruption to local residents and I would like to thank them for their understanding and co-operation as our enquiries continue.
"The victim is being supported by specially trained officers and is being kept updated as the investigation progresses."
Anyone with information, or video footage, that may help with the investigation is asked to contact DS Dunn by emailing firstname.lastname@example.org quoting incident 19 of 27 November.
Alternatively, contact Crimestoppers anonymously on 0800 555111 or at crimestoppers-uk.org