The death toll has risen to 233 in last week's explosion in a natural gas field in southwest China.

Beijing's official Xinhua news agency reported the additional deaths Sunday, saying 35 more bodies had been found in mountainous villages near Chuandongbei field in Kaixian county in the densely populated city of Chongqing.

Meanwhile, some of the more than 42,000 people evacuated from a 25 kilometer square area around the blast site began returning home, as investigators tried to find out what caused a well to burst and spew poisonous gas for four days.

Technicians capped the well Saturday, stopping the flow of sulphurated hydrogen that turned the surrounding area into a death zone.

More than 9,000 people were poisoned or burned by the fumes, and Xinhua says about 10 percent of them remain hospitalized.

About 1,000 health workers and soldiers have begun a cleanup in the area, carrying away thousands of animal carcasses and disinfecting several villages.