Police in Birmingham have said a man apparently attacking women with hypodermic syringes has claimed at least 11 victims.
Detectives launched a manhunt after a woman complained about a sharp pain in her thigh, which later turned out to be a puncture wound.
West Midlands Police released a CCTV image of their prime suspect and have launched an appeal to find a man who "could hold vital information" to help apprehend the attacker.
Investigators initially said they had five reports of women being attacked with needles in Birmingham. DI Julie Woods said: "We have received five reports in total over the last year and a half and although the women have not been left with any obvious physical injuries they have had to endure an agonising wait to check that they have not suffered any long-lasting health effects.
"Whilst we have been unable to confirm exactly how the injuries were caused, it is believed that a hypodermic needle may have been used on each occasion, with young women being specifically targeted.
"Due to the nature of the offences, victims may have not realised they have been injured until hours or days later, which has resulted in limited lines of enquiry. But we now have a particularly clear image of a man we want to identify in connection with the attacks and I would appeal for him, or anyone who knows who he may be, to come forward."
Police said a further six women had come forward to report similar attacks in the city centre.
Woods said: "We have received several calls with information following the appeal on Friday and are following these up.
"These are strange offences and the motive at is unclear but we do not underestimate the anxiety and stress that the attacks can cause."
She added that the man they wish to speak to, circled in green in the photograph, may have witnessed the attack or knew the person responsible.
Supt Danny Long said that extra patrols were on the streets.
"We have increased the number of officers on patrol in Broad Street and around the city centre, particularly since the attack earlier this month, and are working closely with street wardens, street pastors, licensees, door staff and clubbers themselves to keep people safe," he said.