Many bogus $1,000 banknotes are feared to be in circulation after 217 counterfeit notes were discovered at two banks in Sheung Shui yesterday. A youth, 16, and his father, 42, were among five people arrested in connection with the cases. They told police they collected the money during business transactions on the mainland. In Sheung Wan, a sixth male suspect was arrested after he tried to deposit $60,000 at the Yien Yieh Commercial Bank in Des Voeux Road Central yesterday afternoon. Some of the banknotes were suspected to be forgeries. The first batch of forgeries surfaced when the youth tried to deposit $100,000 in cash at the Yien Yieh Commercial Bank in San Fung Avenue, Sheung Shui, yesterday morning. Police were called in when cashiers suspected 40 out of 100 banknotes were forgeries. The teenager was arrested inside the bank and his father was found outside. Police seized $1.2 million in cash from the pair. They told officers the money had been collected from a business transaction on the mainland, claiming they sold seafood there. As police made inquiries at the bank, another cashier found 50 suspected fake notes when a man, 18, and his mother, 46, said they wanted to deposit $100,000. The woman claimed that the money was also collected on the mainland, where she sold mobile-phone accessories. Staff from the nearby Sin Hua Bank called police after they discovered 51 suspect banknotes after a woman, 44, tried to deposit $100,000. She told police she was depositing the money on behalf of her boss, who ran a trading company in Sha Tau Kok, at the border, and had business transactions on the mainland. Assistant Sheung Shui divisional commander (crime) Acting Senior Inspector Wong Poon-yam said the 141 banknotes seized from the two banks were confirmed to be forgeries and the $1.2 million seized from the 16-year-old boy and his father contained 76 fake notes. All the fake notes were in $1,000 denominations. Detective Inspector Law Poon-chuen from Sheung Shui police station said: 'The parties claim they do not know each other . . . all three parties tried to deposit the same amount - $100,000 - and all claimed their money was collected during business transactions in China.' The head of the Commercial Crime Bureau, Acting Chief Superintendent Peter Else, said it was the largest number of fake banknotes seized in a single day. He said people should look carefully at banknotes if they doubted their sources. Earlier this year, a counterfeit expert, Chief Inspector Michael Yu Shi-cheung of the Commercial Crime Bureau warned that more than 100 fake $1,000 banknotes they had seized were of good quality and could not be detected easily. All six people were being questioned last night.