Reuters earlier reported that the Singapore-based firm was set to announce a strategic partnership with a Japanese peer, after Olam, majority-controlled by state investor Temasek Holdings, halted trading of its stock on Thursday.
One of the sources said Mitsubishi had done extensive due diligence and had also looked at other strategic investments before choosing Olam. The people declined to be identified as discussions were private.
Olam, in which Temasek holds a 58 percent stake, will sell new shares to Mitsubishi as part of the transaction, in which Temasek's stake will be diluted. Olam's founding family will also cut its stake in the company, the source said.
In a stock exchange filing on Thursday, Olam requested a trading halt pending an announcement. A Mitsubishi official had no immediate comment and Temasek declined to comment.
Olam processes and sells foods such as nuts and spices, as well as raw materials such as cotton and rubber.
The people said Olam had held talks with Mitsubishi and Mitsui to form a joint venture and use the Japanese firms' global reach. The talks included one of the Japanese firms investing in Olam, they said.
Mitsui declined to provide immediate comment.
Temasek raised its stake in Olam after the agri-trader's accounting practices were criticized by short-seller Muddy Waters in late 2012, sending Olam's share price sharply lower.
Olam, with a stock market value of $3 billion, has since sold stakes in more than a dozen operations, including in grains and dairy, to cut debt, boost cash flow and generate profits.
The people said an announcement on the partnership could come as early as Thursday.
Olam's shares were 13 percent higher before the halt, on track for their biggest single-day percentage gain in more than six years. The broader market rose 2.5 percent.
The deal also boosted shares of Noble Group, the Singapore-listed commodities trader that has also come under fire from Muddy Waters among others. Noble's shares, down more than 54 percent year-to-date, were up almost 5 percent at 0.54 cents each in afternoon trade.