Monsanto said it received a unsolicited mini-tender offer on Tuesday by TRC Capital Corp. to purchase 2 million shares of stock at $54.15 per share. That offer, the company said, is 5.5 percent below the $57.30 Monsanto’s shares were selling by closing price on Tuesday.

Monsanto urged shareholders on Wednesday to seek financial advice before responding to the below-market offer.

Mini-tender offers are offers for less than five percent of a company’s stock. They aren’t subject to the same disclosure and procedural protections than larger-scale tender offers, and “have been increasingly used to catch investors off guard,” according to the U.S. Securities and Exchange Commission.

“Monsanto shareowners who already have tendered their shares are advised that they may withdraw their shares by providing the written notice described in the TRC offering documents prior to the expiration of the offer,” the company said in a statement.

TRC’s offer is set to expire on Nov. 17.