China's Guangdong province will order more than 900 factories to close by Friday for failing to comply with new rules on producing dangerous chemicals, Hong Kong's trade office in the province said on Monday.

Under national rules issued in December, 2,040 factories in southern Guangdong that produced dangerous chemicals had until the end of that month to apply for safety production certificates, Hong Kong's Economic and Trade office in Guangdong said.

About 1,100 factories would have obtained the required certificate by a June 30 deadline, it said in an e-mailed response to questions from Reuters.

"The remaining 900-strong factories would be required to cease operation after the deadline," it said.

Among them were some Hong Kong factories, but the trade office did not know how many. Hong Kong borders Guangdong.

Guangdong has been at the heart of China's economic revolution since reforms began in the late 1970s and it has evolved into a major global manufacturing hub with thousands of plants producing everything from cars to crackers.

Workers rights groups have complained that many of the region's factories are dangerous and work conditions are poor. Others are serious polluters.

C.K. Liu, an official with the trade office, said the new rules aimed to upgrade production standards but were not directly related to the environment.

An officer at the information department at Guangdong's environmental department said he was not aware of the new regulations.