Search parties had been looking for 22-year-old Luke Jobson, who disappeared in Yarm, Teesside, in the early hours of Saturday.
On Tuesday, Cleveland Police said that a body found in a river on Monday, near the spot where Mr Jobson disappeared, has been confirmed as the trainee engineer.
A spokesman added that five males who came forward following police appeals have been arrested on suspicion of manslaughter.
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Officers said two aged 18 and two aged 16 have been released under investigation, while another 18-year-old remains in custody facing questioning.
Police said on Monday that one line of inquiry was that there had been an altercation outside the Keys pub in Yarm, and appealed for anyone with dashcam footage to contact them.
Dozens of people turned out to help search for Mr Jobson after his disappearance, and had to be warned by police to stay away from the area around Yarm School in order to allow specially-trained officers to do their work.
A Facebook appeal for help to find him was set up by his aunt and was shared more than 60,000 times.
Asking for help, she wrote: ‘Luke needs to be found and needs to be home, fast. He is 22, he wouldn't hurt a fly, he is a popular, happy, calm lad that needs to be found ASAP.’
A police spokesman added: ‘We are aware of various rumours and speculation circulating on social media but we would stress that sharing these further can be very distressing for Luke's family as well as being unhelpful to our ongoing inquiries.’