A Prison Service spokeswoman said: "An incident at HMP Long Lartin on Thursday February 14 resulted in the death of prisoner Subhan Anwar.
"Two prisoners are now in police custody and the matter is being investigated by police."
More top news
Longest cold spell of winter so far. Bitterly cold with further wintry showers, significant snowfall likely over hills
Demonstrators will gather in Lincoln this morning to protest against proposed cuts to the city's local fire service.
Jon Mitchell with tonight's weather