An uncle-nephew duo have been arrested on the charge of duping at least six traders of “unaccounted cash” adding up to Rs 1.1 crore that they had wanted to turn legal.

Police said each trader had given around Rs 20 lakh to Sanjay Jain, 50, and nephew Nitin Sau, 30, who ran a chartered accountancy firm in Chowringhee Lane.

“The deal was that the duo would return the money to the traders through account-payee cheques. Jain and Sau would get 1.5 per cent of the cash deposited as their commission,” said Tripurari, deputy commissioner of police, central.

On Thursday afternoon, Abhishek Mohnka, a garments trader from Dum Dum, had deposited Rs 20 lakh with the Chowringhee Lane firm. Mohnka was asked to come back in the evening to collect his cheque. But when he went there, Jain claimed the money was with Sau and Sau claimed it was with Jain.

“When Mohnka threatened to call police, the duo confined him in the office,” said an officer of New Market police station. During the confinement, Mohnka managed to call a relative, who alerted the police. “We rescued the trader after midnight,” the officer added.

Sleuths came to know the duo had cheated at least five others. The accused were sent to police custody till May 12 but Jain has been released on bail on medical grounds.