Beijing may be reluctant to reveal who died in Sunday's ethnic clashes in Xinjiang's capital, Urumqi , for fears the news will stir up ethnic hatred, mainland experts say. Six days after the start of the worst ethnic violence in decades, Beijing has still not revealed the identities of the dead. The lack of information has frustrated many, and raised questions. The authorities have not updated the death toll of 156 since late on Monday, although sporadic killings have been reported in the media. Most independent media reports have agreed that the vast majority of people killed on Sunday were Han Chinese. British newspaper The Times identified 33 of those killed as Uygurs and the rest as Han Chinese. Some reports have claimed many Uygurs were killed on Monday when thousands of angry Han flooded into the streets of Urumqi in protest, but western journalists, many of whom witnessed the Han protest, found no evidence to back up these claims. Mainland experts said they believed the main reason behind Beijing's reluctance to release the information was worries that it might lead to fresh clashes. Hu Xingdou , a professor at the Beijing Institute of Technology, said authorities must think carefully about the timing of the release of any information given that the situation in Urumqi remained tense. 'If the government comes out and openly says most of the killed people were Han, or Uygur, it would not be good for maintaining stability,' he said. He said the official silence could also be because authorities were still identifying victims. As in other big mainland cities, a significant number of people in Urumqi are migrant workers, whose identities can be hard to confirm. But some experts said not releasing information could also be risky. It would give ammunition to pro-independence Uygur activists who might accuse Beijing of a cover-up, they said. The World Uygur Congress, headed by Uygur businesswoman Rebiya Kadeer, who lives in exile in the United States, has estimated that more than 400 Uygurs were killed, without providing any other details. Liu Junning , a Beijing-based political commentator, said public anxiety over the riots arose out of the fact that the mainland had no transparent or independent mechanism for investigating major public events. 'Without a credible information-releasing mechanism in place, we don't know when we can get the truth or that what we'll be given is trustworthy,' he said.