Police work is ongoing “at a number of locations” in Lincolnshire and Nottinghamshire, officers say.
Investigations are taking place in Lincolnshire and Nottinghamshire after a 28-year-old man died following an altercation in the grounds of a National Trust property.
Lincolnshire Police said the victim was involved in an assault at Belton House, near Grantham, on Thursday in an area not open to the public.
The force said the man returned home but later became unwell and died.
A 29-year-old man arrested on suspicion of murder has been released on bail.
Police said work was ongoing “at a number of locations” in the two counties, including at Belton House.
“Part of our investigation is around establishing the exact cause of death, which will be done following a formal Home Office post mortem examination at some point next week,” a force spokesperson said.
Officers previously said it was believed the people involved knew each other, with the incident not involving National Trust staff or Belton House visitors.