The accused told Sharifuddin, a cloth merchant from Bihar, that they would get his demonetised currency notes exchanged with new ones, a senior police officer said.
He had given them Rs 18 lakh, but did not get the new banknotes in return, following which he filed a complaint at Tilak Nagar Police Station on November 22, the officer said.
After an inquiry, Sudhir Rathi, a sub-inspector posted at Kalyanpuri Police Station, along with three others, Rannvijay, Rohit and Ankur, were arrested this morning, police said.