A solicitor who was found dead after going out jogging had suffered stab wounds.
The body of Peter Thomas Maine, 56, from Wynyard, Stockton-on-Tees, was found near the running track of Maiden Castle Sports Centre, Durham.
He was under investigation for fraud by Durham Police in connection with his job as a lawyer, it has emerged. The Solicitors Regulation Authority had also launched an investigation into his conduct.
Durham Police said the death was unexplained and have launched what they called a "murder-style inquiry".
Officers want to trace a young couple who were camping near Maiden Castle overnight. They were thought to have been picked up by a car around the time an ambulance arrived treat Mr Maine, who suffered puncture wounds to the chest.
In a statement the family of the married father of two said: "Peter was a loving husband to Joanna, a devoted father to Lucy and Jessica and a much-loved son of George and brother to Helen.
"Words at this time cannot express how we, his family, are feeling. We would ask that anyone with information regarding what happened to Peter to please contact Durham constabulary. This is a very difficult time for us, his loving family, and we request that we be afforded privacy in order to try to come to terms with our very sad loss."
The area was cordoned off as officers from specialist search teams, including marine experts, carried out extensive searches of the River Wear and its banks.
Mr Maine's black Land Rover Discovery had been parked in the city centre's Old Elvet just before 7.30am.
Durham Police have appealed for anyone in who was in the area between 7.15am and 8.15am to come forward.