Lawmakers had asked the IG to look into "potential instances of suppression and alteration of scientific reports, documents, or communications" produced by USDA.

POLITICO revealed one case in which USDA officials had tried to dissuade research partners at a university from disseminating their findings about how rising carbon dioxide levels in the atmosphere led to a drop in key nutrients in rice, the world’s most important crop.

A leading USDA crop scientist ultimately resigned from the department over the incident.

“You get the sense that things have changed, that this is not a place for you to be exploring things that don't agree with someone's political views,” Lewis Ziska, a leading plant physiologist said in a wide-ranging interview in August. “That's so sad. I can't even begin to tell you how sad that is.”

The investigation will examine whether any changes in policy or processes affected the publication of science or the communication of any research results. It will also look at changes in resources and staffing levels, suggesting that the probe could be quite broad.

In a letter to Pingree on Monday, Phyllis Fong, USDA's IG, noted that there are broader concerns that USDA's recent relocation of the Economic Research Service and the National Institute of Food and Agriculture to Kansas City were "used as a means to suppress research on controversial topics such as climate change," a situation that POLITICO also reported on last spring.

Roughly two-thirds of positions at ERS are now vacant after the administration moved the agency to the Midwest on short notice.

Democrats lauded the news that a formal investigation has begun.

"Across the government, inspectors general are playing a crucial role in holding this administration accountable, and I want to thank Inspector General Fong for initiating this important investigation," Hirono said in a statement to POLITICO.

Pingree, a Maine Democrat who serves on the House Agriculture Committee and the appropriations panel that funds USDA, also praised the move.

"From droughts to floods, farmers are under threat across the country because of increasingly unpredictable weather events," she said. "The allegations that the Trump administration has suppressed USDA research which could help us mitigate the impacts of climate change raise very serious concerns."

The news of the IG investigation follows another report from POLITICO last week, which found that USDA is spending less than one percent of its budget helping farmers and ranchers adapt to climate change while weather becomes increasingly extreme and unpredictable across the country. The climate work that continues on a shoestring budget at USDA is being kept low-profile to avoid political controversy.