Police have detained six suspects after busting a secret counterfeit mask production base in Foshan's Nanhai district of South China's Guangdong province on Jan 30.

Workers make protective facial masks at a subsidiary of Alibaba Group Holding Ltd in Guangzhou, capital of Guangdong province. (Photo: China Daily)

Three sets of production equipment, plus 175,000 fake N95 masks and 80 cases of raw materials, were seized in the den, according to a statement released by Guangdong Provincial Department of Public Security on Friday.

"None of the fake masks have entered the local market so far, thanks to a timely crackdown on the case," a police officer was quoted as saying.

Local police immediately set up a special task force and launched a further investigation after local residents reported that a secret factory located in Baidong village in Xiqiao township was still in full production at midnight on Jan 29.

And a police operation was immediately launched in the early morning on Thursday, said the officer.

"All the windows and doors of the two-story factory were closed when police arrived on the scene," the officer said.

The police officer urged locals to buy masks from authorized stores and channels to shun buying fake products.

Investigation of the case is still ongoing, the officer added.