The People's Bank of China, the mainland's central bank, has released a chart in a rare move to help the public spot fake banknotes amid growing disquiet over an influx of counterfeits.
The chart identifies some 13 features that distinguish a real banknote from a counterfeit.
Sophisticated fake 100-yuan banknotes, most of them with serial numbers beginning with HD90, first turned up in Guangdong this month.
Others have been spotted in Hong Kong, Shanghai, Beijing, Hunan , Guangxi , Sichuan and other parts of the country in the past few days, triggering widespread concern on the mainland.
The bank's Shanghai branch, which oversees issuing notes, said it was investigating and promised to make its findings public in the coming week.
In a statement dated Friday, the central bank denied that the fakes were a new type developed with sophisticated technology, saying a trained eye could still spot them. It said mainland commercial banks began to notice the counterfeits as early as 2007 and, by the end of October, the central bank had issued an internal directive ordering the banks to upgrade infrared machines to detect the counterfeits.
Speaking in Shenzhen after meeting Hong Kong delegates to the National People's Congress and the Chinese People's Political Consultative Conference, bank governor Zhou Xiaochuan said officials were strictly curbing the production of counterfeit notes, and he believed the issue would not become a large economic problem.
A resident of Mianyang , Sichuan, told Chengdu Business Daily that nine of the 10 100-yuan banknotes he withdrew from an ATM were counterfeit and each bore a HD95 serial number.
The report quoted Pan Jun , office director of a joint State Council commission tackling counterfeit banknotes, as saying that most of the mainland's makers of infrared banknote machines did not meet product technical standards, leaving the public defenceless against the influx of imitators.
Renmin University public policy professor Mao Shoulong said the central bank needed to increase transparency because it took nearly two years to inform the public.
Media reports claim the counterfeit notes largely originated in Taiwan.
Cross-strait smuggling has been a recurring problem for years, despite authorities developing new security features to beat counterfeiters.