OLDWICK, N.J. Bus and limousine insurer National Indemnity Co. of Omaha, Neb., has been put on credit watch, along with other insurance subsidiaries of Berkshire Hathaway Inc., by several credit and insurance rating services.

The rating moves came after Berkshire Hathaway announced it was acquiring Burlington Northern Santa Fe Corp. for $100 per share in cash and common stock, making it the 100 percent owner of the railroad.

The transaction is valued at $44 billion and includes the assumption of $10 billion of BNSF debt.

Insurance rating service A.M. Best said it initiated its review because it has concerns "regarding the utilization of (Berkshire Hathaway's) insurance and reinsurance operations as a funding source for this transaction."

Best said it also is "concerned with the liquidity and concentration risk pertaining to a single large investment as a substantial portion of (Berkshire Hathaway's) portfolio, since the majority of (Berkshire Hathaway's) equity investments are held at the insurance and reinsurance entities."

In taking action, Best joined Standard & Poors and Fitch Ratings in placing the "financial strength ratings" and "issuer credit ratings" of the domestic and international insurance subsidiaries of Berkshire Hathaway under review with negative implications.

Best placed the financial strength ratings of 'A++' (Superior) and issuer credit ratings of "aaa" of National Indemnity Group and Government Employers Group (GEICO) and their members under review with negative implications.

In addition, it placed the financial strength ratings of 'A++' (Superior) and issuer credit ratings of "aa+" of General Re Group and its members under review with negative implications.

Best will reassess the under-review status as more details regarding the capitalization and liquidity of the insurance and reinsurance operations is presented by Berkshire Hathaway management.