WASHINGTON (AP) — A new Associated Press investigation, which found that ethanol hasn't lived up to some of the government's clean-energy promises, is drawing a fierce response from the ethanol industry.

In an unusual campaign, ethanol producers, corn growers and its lobbying and public relations firms have criticized and sought to alter the story, which was released to some outlets earlier and is being published online and in newspapers Tuesday.

Their efforts, which began one week before the AP project was being published and broadcast, included distributing fill-in-the-blank letters to newspapers editors that call the AP's report "rife with errors." Industry officials emailed newspapers and other media, referring to the AP's report as a "smear," ''hatchet job" and "more dumpster fire than journalism."

"We find it to be just flabbergasting. There is probably more truth in this week's National Enquirer than AP's story," said Geoff Cooper, vice president of research and analysis for the Renewable Fuels Association in a press call with reporters Monday criticizing the investigation.

The economic stakes for the industry are significant. Congress is working on legislation to do away with the corn-based portion of the mandate, which required oil companies to blend billions of gallons of ethanol into their gasoline. Big Oil is pumping big money into the effort. The Obama administration, a strong defender of biofuels, is soon expected to slightly ease the law's requirements. Overnight, such changes would eliminate a huge source of the demand for ethanol, reduce profits for farmers and ethanol producers and likely lower the price of corn.

The AP's investigation is based on government data, interviews and observations. It highlights what many researchers have published in peer-reviewed journals and is consistent with reports to Congress by the Environmental Protection Agency about ethanol's environment toll.

"The AP's reporting on this important topic is a result of months of work and review of documents, and interviews of experts and people on all sides of the public policy debate about this energy resource," said Mike Oreskes, AP's vice president and senior managing editor. "We stand behind our reporting and welcome further insights and discussion."

Specifically, the ethanol industry disputed AP's findings that as farmers rushed to find new places to plant corn, they wiped out millions of acres of conservation land and destroyed habitat. The industry said the primary driver for such losses was Congress lowering the number acres allowed in conservation, not ethanol. It also cited a Dutch study, which was not peer-reviewed and found that urban sprawl internationally was responsible for greater loss of grassland than biofuels.

In addition to citing the Agriculture Department's figures of more than 5 million acres of conservation land transformed under the Obama administration from grass field back into farmland, the AP analyzed U.S. government crop data collected by satellite. The AP identified tracts of land that were cornfields in 2012 and had been grassland in 2006. The AP then excluded land lost from the Conservation Reserve Program to prevent double counting. The AP vetted this methodology with an independent scientist at South Dakota State University, who has published peer-reviewed research on land conversion using the same satellite data.

The Dutch study that the industry cited, which AP did not mention, noted that in the United States "biofuel expansion is the dominant cause of agricultural land use loss."

The ethanol industry said farmers were not converting native grasslands into cropland. The AP cited USDA's own data for 2012, the first year it collected data on so-called new breakings, showing that 38,000 acres of never-before-planted grassland was farmed.

The ethanol industry also complained that AP was misleading when it said since 2010 more corn went to fuel than livestock feed. It noted that the distillation process leaves behind a residual byproduct that can be used for feed. The AP used the government's official, long-established benchmark for domestic corn use: data from USDA's Economic Research Service, which do not factor distiller's grain into its official data. The figures show that, in 2010 for the first time on record, fuel was the top use of domestic corn — a trend that continued in 2011 and 2012.

Monday's press call criticizing the AP also included Leroy Perkins, an Iowa farmer interviewed for the AP project. Perkins said he was surprised by the article's focus. He said he thought the AP was writing about the increase in farm ownership from people outside the area and about water quality impacts.

An AP spokesman, Paul Colford, said Perkins was clearly aware of the questions that AP had about the expansion of cornfields into conservation land and went out of his way to be helpful, even helping AP arrange a flight over Iowa farmland. Colford said that, like many other farmers contacted by AP, Perkins said he would prefer to keep land in the conservation program but was reconsidering, given the favorable price being offered for corn.