A 40-year-old man has died after he was arrested by police in the early hours of Wednesday, September 29.
The man, from Gainsborough, was arrested by officers on suspicion of a breach of the peace offence at around 1am.
Lincolnshire Police said he was taken ill while he was being transported to a custody suite.
Officers stopped on Riseholme Road in Lincoln to give him first aid.
Additional police and ambulance crews were called to the scene, but the man died shortly afterwards.
An investigation is ongoing to examine the exact circumstances of his death, Lincolnshire Police said in a statement.
The matter has been referred to the Independent Office for Police Conduct.