A man has been arrested in connection with the death of a partygoer who is thought to have died after taking part in a game of "Punch 4 Punch," which involves two people being filmed trading blows until one of them gives up.
Tommy Main, 23, is said to have collapsed as he was filmed playing the game at his home in Erith, south east London.
The game has gained popularity after footage of the bouts have appeared online, with losing participants generally given a forfeit, such as downing a drink.
Police and ambulance crews were called to the incident in the early hours of Sunday morning and the father-of-one was taken to hospital in a critical condition, but died shortly afterwards.
A 20-year-old man who was arrested by police investigating the death has been bailed until September and detectives are appealing for people at the party who may have videos of the incident to come forward.
Lead investigator Detective Inspector Michael Norman said: "Tommy's death is being treated as unexplained but I would urge any of his friends who were at the party on the night of his death to make contact.
"I am especially interested in any images or footage from the nights of his death."
Mr Main's brother, Roy, 36, shared a video tribute to his sibling and used his own Facebook page to criticise people at the party who were filming at the party but who he said did nothing to help his brother.
"I had to say good by to my little brother today for the last time," he wrote. "I'm hurting so bad I'm so sad I love you tommy main ... I don't think ill ever be the same again.
"For the people that was at the party that can see this call your self friends ... you should have stoped it not try and film it."
A post mortem examination proved inconclusive and detectives are now awaiting the result of toxicology tests.