One week after unrest between Muslim Uighurs and Han Chinese in the Chinese city of Urumqi left more than 180 dead, an explosion at a chemical factory on the outskirts of the city today raised tensions between the ethnic groups again. But local police have ruled out foul play.

An earlier statement said the fire had been quickly extinguished and there were no casualties. It said the company was still investigating the exact reason for the explosion in which an oil tanker blew up.

Xinjiang's eight million Uighurs say they are discriminated against under Chinese rule. Last Sunday, Uighur protesters attacked Han Chinese, who took to the streets of Urumqi early in the week wielding machetes, poles and chains vowing vengeance.

The main square in central Urumqi is still closed, with riot police surrounding it. Security forces are continuing to patrol Urumqi's streets. Elsewhere in the Xinjiang province, strict security measures are still in place.

Photo of Urumqi streets by EPA