Police forensic officers are carrying out enquiries at Blagdons Meadow in Plymouth this morning.
A police vehicle and forensic services van are at the open space off Embankment Road, with officers concentrating their attention on an area around bushes within the meadow.
A police officer is guarding the area while a forensic officer, wearing protective clothing, is photographing the scene and appears to be taking samples.
An eyewitness who regularly swims in the area said he had seen several people at the meadow last night.
The eyewitness said he believed that officers were investigating a possible Rape, although this has not been confirmed by police.
A second eyewitness also described significant police activity in the area overnight.
At this stage, the circumstances surrounding the police presence are not known and Devon and Cornwall Police have not confirmed the nature of the incident.
Plymouth Post has approached police for further information.
Photographs © Wayne Perry / Plymouth Post