Police are appealing for information following reports of a possible serial flasher who is thought to have been targeting women in Hyndburn since 2011.
Officers are now investigating a total of 13 similar incidents that have taken place across the Hyndburn area. The incidents all involve a man exposing himself to women who are inside their properties with the lights on and curtains open at the time, say police.
A spokesman for Lancashire Police said: "The first offences were reported to police in 2011 and took place in Oswaldtwistle and on Lime Road in Accrington. They were followed by a further incident which took place in 2012 in Knuzden.
"In 2013 there were six reported offences which all took place in Accrington on Kings Road, Owen Street, Devonshire Street, Hereford Close and Gloucester Avenue.
"There were a further three incidents reported in 2014, one which took place in Oswaldtwistle and two which took place in Accrington on Lemonius Street and Devonshire Street. An appeal for information was issued at the time but no similar offences were reported until last week.
"The most recent incident happened on Thursday, March 9 when a man approached the front of a house on Winchester Avenue shortly before 10.30pm.
"Patrols in the Accrington area have been increased to provide reassurance to the local community and to deter any further offences."
Officers are appealing to anyone with any information about these incidents to come forward.
DI Tim McDermott of East CID said: “These offences are concerning and extremely distressing for the victims. Whilst we cannot be certain that one man is responsible for all of the offences, their similarity is so striking that we believe they are likely to be linked. These offences are committed after dark so it’s very difficult for victims to provide us with a description and I am appealing to the public to come forward with any information they may have.
“We would particularly like to hear from anyone who saw a man walking in the Winchester Avenue area at around 10.30pm last Thursday evening. Even if the person you suspect is someone you know I would urge you to get in touch with us so that we can protect the public and help whoever is responsible to address their behaviour.”
Anyone with information can contact Lancashire Police on 101 quoting log 1643 of March 9.
Alternatively the independent charity Crimestoppers can be contacted anonymously on 0800 555 111 or online at crimestoppers-uk.org.