Last week, the Securities and Exchange Commission froze a Swiss account linked to possible insider trading in the Heinz takeover, and now the FBI has added scrutiny to the deal.

Like the SEC, the FBI's office in New York, one of the main players behind the government's recent crackdown on insider trading, is examining a series of well-timed trades made a day before Berkshire Hathaway and the investment firm 3G Capital agreed to buy Heinz. The deal sent the company's shares - and the value of options contracts - soaring.

Traders bought 2,533 call options on Wednesday through a Swiss account at Goldman Sachs, according to the SEC, which called the activity a "drastic" uptick in trading for Heinz.

At the time of the SEC's action on Friday, authorities had not determined the identity of the traders, and the FBI declined to comment further Tuesday. Goldman, which is not accused of wrongdoing, was the conduit for the trades. A bank spokesman said Goldman is cooperating with the investigation.

Using what is known as a call option, the unknown traders placed a bullish bet on Heinz without actually buying the company's shares. Instead, the investors have the opportunity to buy the stock at a given price through June.

The anonymous investors spent nearly $90,000 on the call options, a position that skyrocketed on paper to $1.8 million after the deal was announced Thursday. At the time, Heinz's stock rose to $72.50, up 20 percent from Wednesday, matching the offer price.

"The timing, size and profitability of the defendants' trades, as well as the lack of prior history of significant trading in Heinz" in the account, "makes these trades highly suspicious," the commission said in the complaint.