The Enforcement Directorate on Friday conducted searches at half-a-dozen locations in Tamil Nadu in connection with its money laundering probe into a case of alleged irregularities in the issuance of visas to 263 Chinese nationals in 2011, which also involves Congress MP Karti Chidambaram, officials said.

The premises of some companies and their promoters are being raided in Chennai and nearby areas, they said.

The ED had initiated a probe in May and filed a case under the Prevention of Money Laundering Act (PMLA) after taking cognisance of a first information report (FIR) registered by the CBI in the same case.

The case pertains to allegations of Rs 50 lakh being paid as kickbacks to Karti and his close associate S Bhaskararaman by a top executive of Vedanta group company Talwandi Sabo Power Ltd. (TSPL), which was setting up a power plant in Punjab, as per the Central Bureau of Investigation (CBI) FIR.

The CBI had raided the premises of the Chidamabram family and arrested Bhaskararaman even as Karti Chidambaram was questioned by it.

Karti Chidambaram, 50, a Congress MP from the Sivaganga constituency in Tamil Nadu, has denied the allegations and said in a statement that "if this is not harassment, not a witch hunt, then what is."

He had said he was "certain that he never facilitated even a single Chinese national in their visa process, let alone 250."

According to the CBI, the work for setting up the power project was being executed by a Chinese company and was running behind schedule.

A TSPL executive had sought re-issuance of project visas for 263 Chinese workers for which Rs 50 lakh allegedly exchanged hands, according to the CBI FIR.

The agency has alleged that Bhaskararaman was approached by Vikas Makharia, the then associate vice president of TSPL, for the reissue of project visas for the Chinese workers working at the Mansa-based power plant.

The CBI FIR alleged that Makharia approached Karti through his "close associate/front man" Bhaskararaman, the officials said.

"They devised a back-door way to defeat the purpose of ceiling (maximum of project visas permissible to the company's plant) by granting permission to reuse 263 project visas allotted to the said Chinese company's officials," it was alleged.

Project visas were a special facility that was introduced in 2010 for the power and steel sector for which detailed guidelines were issued during P Chidambaram's tenure as the home minister but there was no provision of re-issue of project visas, the FIR alleged.

"As per prevalent guidelines, deviation in rare and exceptional cases could be considered and granted only with the approval of the home secretary. However, in view of the above circumstances, the deviation in terms of reuse of project visas is likely to be approved by the then Home Minister...," it further alleged.

The CBI, in its FIR of May 14, has named Karti, Bhaskararaman, Makharia, TSPL, and Mumbai-based Bell Tools Limited, through which alleged bribes were routed.

The accused in the ED case are the same.

The CBI case was registered under IPC sections 120-B (criminal conspiracy) and 477A (falsification of accounts) and sections 8 and 9 of the Prevention of Corruption Act.

Makharia allegedly submitted a letter to the home ministry on July 30, 2011, seeking approval to reuse the project visas allotted to his company, which was approved within a month and permission was issued, the officials said.

It alleged that the payment of the bribe was routed from TSPL to Karti and Bhaskararaman through Mumbai-based Bell Tools Ltd with payments camouflaged under two invoices raised for consultancy and out-of-pocket expenses for works related to visas for Chinese workers.

Makharia had later thanked Karti and Bhaskararaman in an email, the CBI alleged.