NEW YORK (Reuters) – As the U.S. growing season entered its peak this summer, farmers began posting startling pictures on social media: fields of beans, peach orchards and vegetable gardens withering away.

The photographs served as early warnings of a crisis that has damaged millions of acres of farmland. New versions of the herbicide dicamba developed by Monsanto and BASF, according to farmers, have drifted across fields to crops unable to withstand it, a charge authorities are investigating.

As the crisis intensifies, new details provided to Reuters by independent researchers and regulators, and previously unreported testimony by a company employee, demonstrate the unusual way Monsanto introduced its product. The approach, in which Monsanto prevented key independent testing of its product, went unchallenged by the Environmental Protection Agency and nearly every state regulator.

Typically, when a company develops a new agricultural product, it commissions its own tests and shares the results and data with regulators. It also provides product samples to universities for additional scrutiny. Regulators and university researchers then work together to determine the safety of the product.

In this case, Monsanto denied requests by university researchers to study its XtendiMax with VaporGrip for volatility – a measure of its tendency to vaporize and drift across fields.

The researchers interviewed by Reuters – Jason Norsworthy at the University of Arkansas, Kevin Bradley at the University of Missouri and Aaron Hager at the University of Illinois – said Monsanto provided samples of XtendiMax before it was approved by the EPA. However, the samples came with contracts that explicitly forbade volatility testing.

“This is the first time I’m aware of any herbicide ever brought to market for which there were strict guidelines on what you could and could not do,” Norsworthy said.

The researchers declined to provide Reuters a copy of the Monsanto contracts, saying they were not authorized to do so.

Monsanto’s Vice President of Global Strategy, Scott Partridge, said the company prevented the testing because it was unnecessary. He said the company believed the product was less volatile than a previous dicamba formula that researchers found could be used safely.

“To get meaningful data takes a long, long time,” he said. “This product needed to get into the hands of growers.”