It happened in the early hours of Sunday.
A woman in her late teens says she was assaulted between Heydons Lane and May Terrace between midnight and 1245am on Sunday morning.
Police are now investigating what's alleged to be a "serious" assault.
Detective Inspector Dawn Perriam: “This is an isolated and extremely rare incident and a thorough police investigation is under way.”
The area was cordoned-off until Sunday afternoon as police enquiries took place.
Witnesses, or anyone with information on the incident, is asked to contact police on 101, or email 101@dc.police.uk, quoting crime reference number CR/057720/19.
Alison Hernandez secures third term as police and crime commissioner
How Exeter's traffic troubles influenced council vote
Labour tightens grip on Plymouth City Council power
Radio Exe newsreader to abseil down Exeter Cathedral
Labour retains control of Exeter City Council
