Boston Central Park has been closed to the public while police investigate an assault.
A man in his 40s received serious injuries and was taken to hospital after the incident, which was reported to Lincolnshire Police at around 5pm on Sunday, March 28.
A member of police forensic staff in a white hooded boiler suit was seen walking around the area on Monday, March 29.
No arrests have been made at this stage.
Police said: “The park has been closed to the public while our investigations continue. We will open the park as soon as our investigations conclude.”
Anyone with information should contact police on 101 quoting incident 248 of March 28.