Lincolnshire Police are investigating reports of a serious sexual assault in Lincoln city centre this morning.
The victim of the assault is understood to have left a nightclub on Silver Street at around 2am on Wednesday, September 21, walking in the direction of Pelham Bridge.
She was wearing a black and white checked jacket and black ripped jeans.
Officers believe she was with a man with blonde hair, aged between 18 and 21.
Anyone who was in the Pelham Bridge area, particularly underneath the play park or near to the Siemens car park between 2am and 4.20am should get in touch with police.
People who saw anyone matching the description of the victim should also call police.
Eyewitnesses said that police arrived at the scene at around 5.30am, cordoning off the Siemens car park by 6.45am.
Anyone with any information is asked to call the non-emergency number 101 referring to incident 35 of September 21.
Alternatively contact the charity Crimestoppers anonymously on 0800 555 111.