The CBI today arrested a former assistant director of the Enforcement Directorate for allegedly demanding a bribe from an accused in the National Rural Health Mission scam. N B Singh, who was posted in the Lucknow office of the ED, along with middleman Subhash was allegedly threatening to attach the properties of the accused. They were demanding a bribe of Rs 50 lakh to take a lenient view of the matter. The officer was on May 18 relieved by the Enforcement Directorate but he continued going to office, sources said. A trap was laid by the CBI and the duo were arrested while allegedly taking Rs 4 lakh as a part payment of the bribe. Singh belonged to the Central Excise and Customs service and was posted with the ED. He was handling certain cases related the NRHM scam. The ED is also considering registering a money laundering case against him.