A police cordon remains in place at the scene of a reported stabbing in Boultham Park in Lincoln.
The cordon was put in place from around 8pm on Thursday, July 4 with a forensics team turning up to examine the area later in the evening.
Police said an incident had taken place, but there is not yet any confirmation as to whether or not it was a stabbing.
A man was seen trying to climb over a fence in line with the police cordon before leaving the scene.
An eye witness at the scene later heard police say on radio that the exhibits were all in the vehicle and everyone had been detained. Police were still on site after 10.30pm.
Reporters contacted Lincolnshire Police for further information, but there was no reply by the time of publication.