The government of Kyrgyzstan says it is treating the deaths of 21 people on a Chinese-owned bus as a criminal act.
Nine spent cartridge cases from an automatic rifle have been found in the burnt-out vehicle, leading investigators to believe that the mainly-Chinese victims may have been shot by bandits before the bus was set ablaze in mountains in eastern Kyrgyzstan on Thursday.
The bus was originally thought to have caught fire after crashing into a ravine.
A government commission to investigate the deaths has been set up under the Kyrgyz deputy prime minister, Kubanychbek Dzhumaliyev.
The authorities say they are not linking the incident to small groups of ethnic Uighurs who have carried out assassinations and bombings as part of their struggle for an independent homeland in the Chinese region of Xinjiang, which borders Kyrgyzstan.
From the newsroom of the BBC World Service