The CBI questioned Trinamool Congress' Rajya Sabha MP K D Singh in connection with Narada sting case in which some persons resembling party leaders were seen accepting money, officials said.
Singh arrived at the agency headquarters in the morning and his questioning is going on, they said.
The agency has also called Mathew Samuels, the editor of Narada news, who had provided the recordings purportedly showing alleged payments received by politicians and senior bureaucrats of West Bengal Government.
In the sting operation, which was claimed to have been carried out in 2014, some persons resembling senior TMC leaders are seen accepting money from the representatives of a fictitious company in return for favours.
The CBI had booked 12 top TMC leaders, including MPs and West Bengal ministers, and an IPS officer in connection with the case.
An FIR was lodged for alleged criminal conspiracy under the provisions of the Prevention of Corruption Act dealing with bribery and criminal misconduct.
The maximum sentence for these crimes ranges from five to seven years of imprisonment.