One trade the SEC is looking at took place at 12:06 p.m. on that day, when there was a purchase of options with the rights to buy 200,000 shares of BlackBerry stock at a strike price of $10 a share, the person said.

Later that afternoon, Reuters reported that Samsung had offered to buy BlackBerry for as much as $7.5 billion, valuing its stock at between $13.35 to $15.49 per share, a 38 percent to 60 percent premium over BlackBerry's trading price at the time.

BlackBerry's stock, which closed on Jan. 13 at $9.71, shot up 30% on the news to close at $12.60 on Jan. 14, its biggest one-day gain in years.

The call options, which expired on January 23, were purchased for 10 cents in the trade. They surged on the Reuters story to a high of $2.55. If the buyer had been able to sell the options at that high they would have been able to make a profit of $490,000 on a $20,000 investment. It is unclear, though, whether the buyer was able to sell the options at a profit.

The SEC is investigating whether a source of information provided to Reuters bought Blackberry options, according to the person familiar with the investigation.