NEW YORK—Solid financials, low stock values and a planned change in leadership are factors drawing several bidders for Transatlantic Holdings Inc., including a group that reportedly includes former General Re Corp. CEO Joseph Brandon.

Last week, Transatlantic said in a statement that it had entered into a confidentiality agreement with an unnamed third party that was in addition to similar agreements it already had with Validus Holdings Ltd. and National Indemnity Co., a unit of Omaha, Neb.-based Berkshire Hathaway Inc.

Transatlantic also said it had agreed with Validus not to take any action through Oct. 31 on pending litigation related to Validus' previously hostile takeover bid for Transatlantic.

The bidding for Transatlantic, the ninth-largest reinsurer in the world according to the 2011 Business Insurance ranking, intensified after its planned merger with Zug, Switzerland-based Allied World Assurance Co. collapsed in September.

Mr. Brandon and Dan H. Jester, a former U.S. Treasury Department official, reportedly are part of an investor group that has begun negotiations with Transatlantic.

Messrs. Brandon and Jester could not be reached, and a representative of the New York financial services firm declined comment.

Validus' bid was worth roughly $2.96 billion as of Friday. Aside from its cash-and-stock offer, Validus said it would add $500 million to Transatlantic's reserves.

National Indemnity's $52-per-share bid was valued at about $3.25 billion, an amount Transatlantic rejected, saying its was only 77% of Transatlantic's stated book value as of June 30.

“There are definitely a cadre of (Transatlantic stock) investors anticipating that an offer of at least as high or higher than the last round received will come through,” said Mark Dwelle, an equity insurance analyst in Richmond, Va., at New York-based RBC Capital Markets.

The first round began as President and CEO Robert F. Orlich approached retirement. Transatlantic's senior management began discussions about possible business combinations back in June 2009, according to a U.S. Securities and Exchange Commission filing. Its willingness to sell became known when it announced its plan to merge with Allied World in June.

The competing offers differ.

Berkshire's all-cash offer was higher per share, but rivals provided Transatlantic investors with the opportunity for gains when stock prices improve, said Paul Howard, director of research at Solstice Investment Research L.L.C. in Glastonbury, Conn.

The reinsurer's business appears solid, experts say. A.M. Best Co. Inc. gave Transatlantic an A financial-strength rating, which the rating agency described as reflecting the company's “excellent” ability to meet obligations.

“It's a global, decent-sized reinsurer, and you can apparently get it for a good price,” said a source.

“These sorts of opportunities don't happen often where reinsurance companies get put into play,” said Paul Newsome, an insurance industry analyst at Sandler O'Neill & Partners L.P. in Chicago. “The multiples are really low, so there's attractive economics” at this time, he said.

An investor group has different motivations for bidding than an existing insurance company.

Someone coming into a deal with money to buy out current shareholders typically would be looking more to make a good investment, said James Eck, vp-senior credit officer at Moody's Investors Service Inc. in New York. A merger, on the other hand, would entail the alignment of corporate cultures, operations, businesses and risk exposures. “It's more challenging, but, depending on the merger partners, could make sense strategically,” he said.

Mr. Brandon had been a rising star at Berkshire's reinsurance operation, Gen Re. But then the government alleged that Gen Re helped New York-based American International Group Inc. inflate its loss reserves with a pair of sham reinsurance transactions, identifying Mr. Brandon as an unindicted co-conspirator. Although legal experts said at the time that the prosecutors most likely did not have enough evidence to charge Mr. Brandon, and no charges were ever field, he resigned from Gen Re in April 2008.

Insurance experts see Mr. Brandon's track record as an asset.

“Mr. Brandon has a good reputation as a deal-doer,” Mr. Dwelle said. He noted a “frenzy of allegation” over derivatives and off-balance sheet deals in 2008. Mr. Brandon's run-in with prosecutors was “probably a product of the times as much as anything,” Mr. Dwelle said.

An investor with Transatlantic stock said Mr. Brandon has key business contacts, but the investor remained dubious about whether Messrs. Brandon and Jester could drum up enough backing to win Transatlantic.

Representatives from Validus, Allied World and Transatlantic declined comment.