An investigation has been launched into petroleum giant Esso, after accusations that their gas stations in the southern province are selling substandard gasoline that causes cars to malfunction.

Li Xiangming, deputy director-general of Guangdong provincial committee of economy and information industry, said his committee is giving great importance to the case and has mandated that relevant departments launch a thorough investigation.

"Guangdong, which has registered more than 6,000 finished oil companies, always spares no efforts to fight illegal gas stations and the trading of fake or substandard quality oils," Li told local media yesterday.

Li had suggested that all the Esso gas stations temporarily close for self-inspection on Monday.

But all the 18 Esso gas stations in Guangdong province had resumed their business yesterday after a day's business suspension for self-inspection on Tuesday.

Zheng Yuqing, a press executive from ExxonMobil's Guangdong company, insisted that Esso's finished oil has no problems. ExxonMobil is the parent company for Esso.

But she refused further comment.

Officials had received several complaints from drivers that their vehicles stopped functioning properly when their car tanks were filled with the alleged substandard oil from the Esso gas stations.

Li's committee, along with the Guangdong provincial administration of industry and commerce, organized an emergency meeting on Monday night to discuss how to handle the case.