Police arrested a 39-year-old man in connection with six indecent assaults in Grimsby in recent weeks.
He has been interviewed and released under investigation as police seek to gather more evidence.
The six incidents happened in the last month in Cleethorpes Country Park, Bargate, Littlefield Lane, Sheepfold Street and on a cut-through off westward Ho.
On each occasion a man approached the victims from behind, mumbled something and sexually assaulted them before running away.
Chief Superintendent Darren Downs said: “We are conducting a thorough investigation and continue to follow up a number of lines of enquiry.
“As a result of those enquiries we arrested a suspect. It has been necessary to release him under investigation and we continue appeal for witnesses and information to build our case.
“An increased police presence in the area will remain in order to provide reassurance to residents.”
Anyone with information or any other victims should call Humberside Police on 101 quoting reference 16/21893/18.