The Justice Department is investigating major fertilizer producers for possible price fixing, according to sources familiar with the matter. Nutrien Ltd., Mosaic Co., CF Industries Holdings Inc., Koch Inc., and Yara International ASA are under scrutiny for their pricing practices in the concentrated US fertilizer market.

This probe examines whether these companies colluded to raise prices for phosphate, potash, and nitrogen-based fertilizers. The investigation, run from the DOJ's Chicago office, is in early stages and could result in civil or criminal antitrust violations. With just a handful of companies controlling most US fertilizer supply, farmers have long expressed concern about market concentration.

The investigation comes amid broader government efforts to address rising food costs. Agriculture Secretary Stephen Vaden has publicly accused Nutrien and Mosaic of operating as a "duopoly" that limits supply to inflate prices. While the companies haven't been accused of wrongdoing yet, the probe reflects bipartisan priorities to police conduct that increases costs for farmers and consumers.