Prosecutors said there was no evidence showing that the men had been tortured during their interrogation.
The chapter of the Hong Kong-based gang is considered the biggest group of criminals from outside the Chinese mainland ever to be busted by the Shenzhen police.
The police said the organization had been largely dismantled in March, after 80 key members were arrested and 22 were put in detention.
The gang had been implicated in as many as 100 criminal cases, involving some hundreds of millions of yuan and seriously affected the social order in Shenzhen.
One of the cases involving the Xinyi'an gang was a fight in May 2008 at a nightclub, when the gangsters beat more than 20 people, leading to one death.
Three police officers are under investigation after they were found to have been offering protection and covering up crimes for Xinyi'an, said the local police in October.
The city's police and prosecutor's office did not respond to inquiries from the Global Times Wednesday.
Landmark building should respect the public's feeling