Both the Wall Street Journal and the New York Times are reporting that the FBI has opened a criminal inquiry into trading related to last week’s $23 billion US takeover of H.J. Heinz Co.

The U.S. Securities and Exchange Commission last week froze assets held in a Swiss bank account after a series of options trades made just before Berkshire Hathaway and 3G Capital announced the proposal.

The news sent the shares soaring by 20 per cent.

Options allow a trader to make a bet on the possibility of a sharp rise in share values and provide a much higher rate of return than buying the actual shares.

The Times, quoting the SEC, says the $90,000 in options were purchased through a Swiss account at New York-based bank Goldman Sachs, and soared to a value on paper of $1.8 million.

Goldman is not accused of any wrongdoing and is cooperating with the SEC.

Heinz shares closed down six cents at $72.14 in New York.