Rahul Bhandari, a 1997-batch IAS officer from Punjab cadre, reached the CBI headquarters in the morning and was confronted with his telephonic conversations with Singla which are understood to be related to elevation of Kumar in the Railway Board and his chances of becoming Member (Electrical), CBI sources said.
The sources said the agency is also likely to question three more officials who are part of Bansal's staff.
They said Bhandari's conversations were tapped by the agency after it put Kumar's and Singla's phone on surveillance.
The conversations revolve around Kumar's postings in the Railway Board, they claimed.
The sources said Bhandari could be a crucial link as the conversations are understood to carry reference to Bansal.
The agency sources said a clarification would soon be sought from Bansal with regards to the bribery scandal.
The CBI has arrested eight persons in connection with the alleged bribery scandal.
CBI had arrested Singla for receiving Rs 90 lakh part payment of alleged bribe amount which was paid by Kumar to Singla through middlemen.
The sources said the money was allegedly a part payment of the Rs 10 crore promised for lateral shifting of Kumar from Member (Staff) to Member (Electrical), which is considered a coveted position in the Railway Board.