File photo: Agencies

XI'AN, Oct. 29 (Xinhua) -- Three missing people have been confirmed dead after a vehicle-mounted testing apparatus exploded Sunday at an oil extraction plant in northwest China's Shaanxi Province, killing five, local authorities said Tuesday.

The vehicle which conducted tests at the plant belongs to a privately-run thermal power technology company in central China's Hunan Province.

Five others injured in the blast have been hospitalized and are in stable condition.

The accident occurred at 7 p.m. when the vehicle was returning from an oil well in the Qilicun oil extraction plant of Yanchang Oil Field Co., Ltd. in Yanchang County in the oil and gas-rich city of Yan'an.

The cause of the blast is under investigation.