Swiss authorities said they will aid a U.S. investigation into alleged insider trading in connection with H.J. Heinz Co the day before it was announced that the company would be sold.

Options markets participants noted extremely unusual activity almost immediately after Warren Buffett's Berkshire Hathaway and Brazil's 3G Capital said last Thursday that they would buy Heinz for $23 billion in cash.

Last week the Securities and Exchange Commission (SEC) filed a suit against unnamed traders who it said used a Goldman Sachs account in Switzerland to trade on purported inside knowledge of the transaction.

"We're in touch with the SEC and will, as in all cases of this nature, cooperate to the extent of our legal possibilities," Swiss financial regulator FINMA said in a statement on Friday.

The traded call options - agreements that gives the option to buy the shares at a pre-determined price at a specified date - are also being investigated by the Federal Bureau of Investigation.

Roland Leithaeuser, a Frankfurt-based spokesman for Goldman Sachs, said that the U.S. investment bank is cooperating fully with the SEC's investigation. Goldman Sachs has not been accused of wrong-doing.

Heinz, Berkshire Hathaway and 3G Capital have all declined to comment.

The Brazilian founder of 3G, Jorge Paulo Lemann, has made a home in Switzerland since the 1990s. He has not been implicated in any wrongdoing related to the deal.

(Reporting By Katharina Bart and Oliver Hirt; Editing by David Goodman)