Derbyshire Police are investigating an allegation of a sexual assault in the Goyt Valley.
A 62-year-old woman told the police that she was walking her dogs near Fernilee Reservoir at around 8pm on May 19, when she was approached by two men who assaulted her.
She has described them as both white and in their 30s. One wore an orange t-shirt and one wore a green t-shirt.
Officers have been carrying out inquiries and visiting the area to distribute appeal leaflets to ramblers and dog walkers.
Witnesses or anyone with information should call Operation Diamond on 101, quoting reference 18000230146.
You can also call Crimestoppers on 0800 555 111.