Chinese officials say they suspect that a blast on board a bus that killed 11 people in the restive northwestern Xinjiang region Thursday was caused by explosives.

Authorities Friday confirmed that a mechanical failure was not to blame, but stopped short of saying the explosion was caused by a bomb.

The bus was carrying 19 people at the time of the incident.

A Chinese official told the French news agency that authorities could not rule out the possibility that the explosion was linked to separatists in the region.

Turkic-speaking Uighur separatists have been fighting to re-establish an independent state of East Turkestan in Xinjiang. They accuse the ruling Chinese of political, religious and cultural repression on the minority Uighurs.

Some information for this report provided by AP and AFP.