New Delhi: 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, that also involves Congress MP Karti Chidambaram, officials said. Karti Chidambaram, 50, a Congress MP from the Sivaganga constituency in Tamil …