More than 1,000 residents evacuated after a fire at a natural gas well in northwest China's Shaanxi Province have returned to their homes, even as the fire enters its eighth day, local authorities said Saturday.

The air in Yanchang County, Yan'an City, does not contain the toxic gases of sulfureted hydrogen, carbon monoxide and sulfur dioxide, a county government official said.

The environment in the area has not been polluted as a result of the blaze that started on July 23, the official added.

Equipment to help extinguish the fire is expected to arrive Saturday, the official said.

The fire began at 11:20 p.m. on July 23 as workers drilled a gas field 2,750 meters underground.

The gas well is operated by Yanchang Petroleum Group.

Fire fighters said nitrogen sulfide and carbon monoxide caused the fire.