A Cleveland Police spokeswoman said the 22-year-old man arrested in connection with the incident has been released on bail.
The injured man remains in an induced coma in hospital, police confirmed.
Officers say they have been searching for all evidence from the scene. It is unclear whether they have found the missing penis.
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Sandiford, a former legal secretary originally from Redcar, was convicted of drug smuggling offences and sentenced to death in 2013.
Durham Crown Court heard that one of the male victims suffered a triple-fractured jaw, while left lying in the gutter, unconscious.