CBI sources said Singh's wife Neelam Devi has been examined in connection with the case and the agency might seek permission from the court to question the MLA who is at present in Jail in a separate case.
With assembly elections scheduled to begin next month, CBI action might be seen with political tinge but it has nothing to do with the polls or any other intention than routine investigation, the sources said.
The MLA is named as accused in several cases of murder and rape.
CBI had alleged in its FIR that there were large scale irregularities in award of contracts to various parties by NTPC Limited, Barh Super Thermal Power Plant, Barh, Patna (Bihar).
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In pursuance to this information, a joint surprise check was conducted by CBI alongwith Vigilance branch of NTPC Limited where it was found that large scale cartelisation took place at the time of filing of tenders.
The agency had carried out searches in August at the official premises of a co-accused firm and residential premises of MLA at Patna.