BEIJING - Investigators believe a massive explosion on a truck near the capital of China's tense Muslim northwest that killed 60 people and injured 173 was likely an accident, but have not ruled out terrorism, an official said Saturday.
The truck, which was carrying explosives for disposal, detonated during Friday evening's rush hour on a major road in the western suburbs of Urumqi in Xinjiang province. The blast thundered across the city and sent a thick cloud of black smoke shooting upward, residents said.
More than 200 police, soldiers and medical personnel sealed off the area, sifting through more than 20 scorched and damaged vehicles and buildings for survivors, government officials and the state-run Xinhua News Agency said.
Based on the initial evidence, police believe an accident caused the blast, although they have not excluded terrorism, said an official with the Xinjiang government's foreign propaganda office, who only gave his surname, Zhang.
But the explosion's timing and location - in the carefully guarded heart of a region with a history of separatist violence - has raised doubts about the government's version and fears it might be linked to Muslim separatists waging China's most violent internal rebellion.
''This accident is very strange,'' said Erkin Ekrem, leader of a group advocating separatism for Xinjiang's Uighurs, the region's largest Turkic Muslim ethnic group. He wondered why there were so many explosives near Urumqi.
Premier Zhu Rongji was in Urumqi Saturday, but Xinhua did not report if he was in the city when the blast took place. Rongji met Saturday with a Japanese trade delegation and former U.S. Treasury Secretary Robert Rubin, now an executive with financial giant Citigroup, to promote a campaign to develop China's hinterland.
Xinjiang is an oil-rich region that has long been China's buffer with Central Asia, now awash with Islamic militancy. Increasingly aided by groups in Afghanistan and other neighbors, Uighur separatists have waged a bombing and assassination campaign against Chinese and suspected collaborators.
Although Urumqi is dominated by Chinese and has recently had little unrest, it was the site of Uighur separatists' most sophisticated and spectacular attack: the nearly simultaneous detonation of bombs on three city buses in 1997. Nine people were killed and 68 injured in the attacks.
An employee at the Materials Transport Co. in Urumqi who heard Friday's explosion and ran more than a mile to the scene said he counted 50 to 60 dead and saw the injured lying on roads and sidewalks in numbers too great to count.
At the center of the scene was the charred truck, apparently a military vehicle, said the man surnamed Chen.
Many of the injured were blinded or crippled, a hospital worker said.
Government officials declined to confirm the description, and Zhang at the propaganda office demanded to know who had provided the information.