The incident happened in woodland off Walsall Road, Great Wyrley, shortly after 5pm yesterday, Staffordshire Police said.
The victim, a woman, is currently receiving support from specially-trained officers.
Now detectives are keen to hear from anyone who may have been in the Walsall Road area at around 5pm on Saturday – along with motorists with dashcam footage who may have been travelling through at the time.
Detective Inspector Stephen Ward from Staffordshire Police said: “We’d like to reassure members of the public that we’re doing all we can establish who was responsible for this attack.
“This incident happened in broad daylight and in a popular area for dog walkers so please get in touch if you have any information that could help us with our enquiries.”
Anyone with any information, CCTV or dashcam footage should message Staffordshire Police on Facebook or Twitter quoting incident number 631 of 24 April, or alternatively contact Crimestoppers anonymously on 0800 555 111.