AIG says invests in Tortoise Energy

Plymouth, ENGLAND, , April 14 (Reuters) - American International Group Inc (AIG.N), the world's largest insurer, has made an investment in Tortoise Energy Infrastructure Corp (TYG.N), according to a regulatory filing on Monday.

AIG, in a filling with the U.S. Securities and Exchange Commission, said it acquired Series E 6.11 percent senior notes issued by Tortoise, due April 10, 2015.

AIG said its ownership is both direct and indirect, through a subsidiary, AIG Annuity Insurance Co.

Last Thursday, Tortoise said it completed a private offering of $150 million of Series E senior notes, and will use proceeds to pay down a credit facility, redeem Series D Senior Notes, and partially redeem Series III notes, and Series IV preferred shares.

Overland Park, Kansas-based Tortoise owns a portfolio of master limited partnership investments in the energy infrastructure sector.

It reached the private placement agreement after experiencing the failed auction of some of its securities in February.

The failure of auctions has plagued investors in recent months, as the once liquid securities became hard to sell amid tighter credit markets.

The securities are long-term bonds that behave like short-term debt and have long been popular with conservative investors because they are tax-exempt. States, cities and other agencies issue the securities, whose interest rates reset frequently. (Reporting by Lilla Zuill; editing by Jeffrey Benkoe)