Detectives are holding five people after the body of a Sussex man was found in a river.
A member of the public found the body of Andrew Boyd in the River Nene at Whittlesey, near Peterborough, on Thursday afternoon.
A post-mortem examination showed Mr Boyd, 39, of Tuscany Gardens, Crawley, died from head injuries.
Speaking on behalf of Mr Boyd's family, his brother, Thomas, 45, said everyone was shocked by the death.
He said: "Andrew was an outgoing person whose main passion was American baseball. All who knew him would remember how much he followed it and played it when possible.
"There seems to be no explanation for this death. I would ask anyone who has any information about Andrew and who has not yet spoken to police to contact them without delay.
"All the family would now like the opportunity to be alone at this time, to grieve in private, and would ask the media to respect our wishes."
Five people from the Peterborough area were arrested on Friday morning, a man and a woman both aged 58, a man and a woman both aged 29 and a man aged 22.
Peterborough magistrates granted Cambridgeshire police an extra 36 hours to question the five until this morning. None of them had been charged as the Argus went to press.
Inspector Mark Bruce, of Peterborough CID, said: "It's part of the investigation to find out why Mr Boyd was in the Peterborough area."
Call police on 01733 563232.
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