The indecent exposure happened at around 8.40am on Saturday morning near Clydebank business park on a path overlooking the canal.
Police are now appealing for information to help track down the man, who its reported was “undressed”.
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The suspect is described as being white, around 5ft 10in tall and aged between 40 and 50 years old.
Detective Constable Nic Neeson said: “Enquiries are ongoing and we are appealing to anyone who may have witnessed what happened to contact us.
“Anyone with information is asked to contact police on 101 quoting incident 0846 of Saturday, April 12.
“Alternatively, Crimestoppers can be called on 0800 555 111, where anonymity can be maintained.”
