A 25-year-old man and four women, 25, 40, 46 and 47, were arrested for murder and remain in custody.
Cumbria Police said the victim’s family had been notified and were supported by family liaison officers.
Officers “urgently search” for a black Nissan Navara pickup truck with registration DV15 TZD, asking members of the public not to approach the vehicle if they are seen, but to contact police immediately.
Deputy Chief Constable Andrew Slattery said: “We are asking for the public’s assistance in our investigation into the murder of Lee McKnight.
“Investigators need to hear from anyone, including Lee’s friends and associates, who may have seen him or had information about his movements on July 23 and 24, particularly in the Fusehill Street area.
“Anyone who has seen anything suspicious in the Blackwell Hall area during this time should contact the incident room.
“Anyone with information or with CCTV, dashcam or any other means of capturing the Nissan vehicle or Lee’s movement, especially in the Blackwell Hall area in the early hours of July 24, please contact us. ”
Anyone with information can contact the police by calling 101 and asking for the North Cumbria Crime and Protection Team, citing incident number 36 of July 24.