A highly placed CBI source told : "A complaint against Singh has been received from the Central Vigilance Commission (CVC) of alleged disproportionate property case."
He said the agency the complaint was received about one and a half month ago.
When asked if the CBI has registered a case or initiated any preliminary enquiry (PE) against Singh, he replied: "As of now, we have not filed any case, nor initiated any PE.
"At first, we are verifying the allegations against Singh. On the basis of verification of the complaint, a decision will be taken to register a case or file a PE whichever is necessary."
When pressed further about the contents of the complaint, he refused to share any further details.
Singh, a 1984-batch IPS officer of Union Territories cadre, took over as the ED Director on October 27, 2016 and retired last October.
Under Singh, the agency attached moveable and immoveable properties worth Rs 36,000 crore. Before him, the ED in last the 10 years had attached assets worth only Rs 9,000 crore.
He had been credited with leading some high-profile investigation cases such as the VVIP helicopters case, cases against former Finance Minister P. Chidambaram and his son Karti, Sterling Biotech case and the Nirav Modi and Vijay Mallya money laundering investigations.
Under his leadership, the ED strength increased from 682 staffers to 1,033 in the past three years. He has also been credited in bringing about newer policies for vigilance checks for induction of officials into the ED even as the much awaited 'special investigation incentive' was granted to the agency sleuths on the lines of what is given to CBI investigators.
Six dedicated forensic labs across the country and field forensic kits to quickly clone hardware during raids were also introduced in his tenure.
Before his appointment as the ED director, Singh served in Delhi Police's elite Special Cell. He was instrumental in the computerisation of crime and criminal records and personal information system in the Delhi Police besides cracking several bomb blast cases in the national capital in 2008.
(Anand Singh can be contacted at anand.s@.in)
( With inputs from IANS )