Syngenta has rejected a merger proposal from China National Chemical Corp., according to a Bloomberg report. The Chinese state-owned company is said to have offered about 449 francs a share, valuing the firm at SFr41.7 billion, or $42 billion, according to sources close to the matter. Syngenta said the figure was too low, citing antitrust and political concerns but the two parties are reported to still be talking.

According to London-based investment bank Liberum Capital, a deal with ChemChina could arguably face fewer antitrust hurdles than with Monsanto. It said ChemChina is the world’s seventh largest producer of crop chemicals with a 5% market share, compared with Syngenta’s 19% and Monsanto’s 8%.

Last August, the Swiss agrochemicals company rebuffed a third offer from Monsanto at 470 francs a share, which it said was too low and did not recognize its future potential. Monsanto finally abandoned its takeover attempts to seek acquisitions elsewhere. Syngenta is also talking to other potential suitors, including DuPont, as it explores options for the business.

In a statement posted on its website, the Alliance of Critical Syngenta Shareholders, a group formed in October this year by independent private and institutional shareholders, has urged Syngenta’s board of directors to fulfil its duties by engaging in discussions and fully consider the value created by a sale. It added that, while there have been two very recent merger proposals, the board should “seriously consider a formal auction process with all interested suits to create maximum value.”

Neither ChemChina nor Syngenta have commented on the report.