* FBI joins SEC probe into suspicious options trades
* SEC has already sued unknown traders
* Shareholder claims deal's terms are unfair
By Emily Flitter
NEW YORK, Feb 19 (Reuters) - The FBI is looking into possible insider trading in the options of ketchup maker H.J. Heinz Co before its blockbuster deal last week to be acquired by Warren Buffett and Brazil's 3G Capital, a bureau spokesman said on Tuesday.
Buffett's Berkshire Hathaway and 3G said last Thursday they would buy Heinz for $23 billion in cash. Almost immediately, options market players noted there had been extremely unusual activity the day before the deal was announced.
On Friday, the U.S. Securities and Exchange Commission filed a suit against unknown traders who it said used a Goldman Sachs account in Switzerland to trade on purported inside knowledge of the transaction.
On Tuesday, the Federal Bureau of Investigation said it was joining in as well.
"The FBI is aware of the trading anomalies the day before Heinz' announcement," a spokesman said. "The FBI is consulting with the SEC to determine if a crime was committed."
A spokeswoman for the investor group declined to comment on the FBI's involvement. A spokesman for Goldman Sachs said the bank is cooperating with authorities' investigations.
Swiss authorities have already said they have not been asked to help with the U.S. investigation.
The SEC enforcement action marked the second time in six months regulators had taken aim at alleged insider trading in a deal involving 3G. The first instance, last September, involved a stockbroker trading on inside information related to 3G's 2010 purchase of Burger King.