A man was taken ill after being arrested for being drunk and disorderly.
The 20-year-old was taken into custody in Skegness at around 1am on Friday, August 18 and later moved to hospital when officers became concerned for his health.
It is believed the man had suffered a head injury and officers are currently working to establish how this has happened.
Locations for enquiries currently include Grand Parade in the vicinity of L A Café.
Anyone who has any information is urged to call 101 quoting incident number 27 of August 18.