Kolkata: The CBI, probing the sensational Narada sting footage case, on Wednesday grilled Narada News portal CEO Mathew Samuel for over two hours in connection with the scam that allegedly showed a number of political leaders accepting wads of cash in return for promise to dole out favours to a fictitious company.

Central Bureau of Investigation (CBI) sources said Samuel was summoned to Nizam Palace - the federal agency's office - here to ascertain some details about the video footage of the sting operation.

The agency had earlier sent a notice to Samuel to appear before it for questioning in connection with the case.

In the sting operation conducted by Samuel in 2014, IPS officer S.M.H. Mirza and a number of senior ruling Trinamool Congress leaders -- including Mukul Roy and former mayor Sovan Chatterjee who have since crossed over to the BJP -- were purportedly seen taking cash or asking that money be deposited elsewhere in return for promising favours to the non-existent company, Impex Consultancy Solutions.

Current state ministers Firhad Hakim, Subrata Mukherjee and Suvendu Adhikari, incumbent MPs Saugato Roy, Kakoli Ghosh Dastidar, Prasun Banerjee and Aparoopa Poddar, former state minister Madan Mitra, sitting state legislator Iqbal Ahmed - all belonging to the Trinamool, were also named in the document.

The 13th accused Sultan Ahmed - then a Trinamool MP - has since passed away.

The footage was uploaded by the news portal in March, 2016, ahead of the West Bengal Assembly elections.

The CBI, which took over the probe in 2017 following a Supreme Court order, made its first arrest last month by taking Mirza in its custody.

The CBI lodged an FIR on April 17, 2017, after a preliminary inquiry revealed prima facie material for registration of a regular case relating to criminal conspiracy and under several provisions of the Prevention of Corruption Act.