House Armed Services Committee chairman and Amarillo Congressman Mac Thornberry said Wednesday that a review by a congressional task force into the possibility that U.S. military leaders falsified intelligence about progress against the Islamic State group confirms "numerous problems" at CENTCOM.

An independent Pentagon probe into the issue concluded Wednesday, finding that U.S. military leaders didn't falsify intelligence about progress in the fight against the Islamic State group. Still, it found many analysts strongly believed their reports were distorted to paint a more positive picture of the campaign.

The Defense Department's inspector general spent 16 months investigating complaints from intelligence analysts who alleged that senior officials at the U.S. Central Command were reworking reports to offer a more upbeat view of U.S. operations in Iraq and Syria between mid-2014 and the fall of 2015.

Investigators said retired Army Gen. Lloyd Austin III, who headed CENTCOM at the time, denied the allegations. He told the inspector general he had no knowledge "of anybody trying to downplay or rosy-up intelligence."

"You're not going to win if you don't have the right information," Austin told investigators, according to the report. "So rosying up - that doesn't help us be successful in this fight."

IS, a spinoff of al-Qaida's branch in Iraq, seized large swaths of territory in Iraq and Syria beginning in 2014. After its quick ascent caught Iraqi forces and the U.S. off guard, the Obama administration pledged to degrade and destroy the group.

Spreading from its headquarters in Syria, IS seized several cities, including Mosul, the second largest city in Iraq, leading to busy, long days at the CENTCOM intelligence unit in Tampa, Florida. (One analyst told investigators that he was so tired that he looked down at his feet while driving to work and realized that he had forgotten to put on shoes).

The allegations by two senior intelligence analysts alleged that leaders were changing reports prompted one of the largest investigations in the Defense Department inspector general's 34-year history. It involved more than 30 personnel, 150 interviews and 17 million documents and files. Approximately 2 million emails were reviewed.

Among the allegations: Claims senior intelligence leaders "arbitrarily adjusted estimates of IS strength;" changed a report on an IS attack at a U.S. air base in western Iraq after it was "considered too critical" of Iraqi security forces; suppressed information regarding a battle at Ramadi, Iraq, in April 2015; and suppressed a report of a massacre by IS forces in Hit, Iraq.

"We did not substantiate the most serious allegation, which was that intelligence was falsified," said the document, which totaled 542 pages in its classified form. The publicly released, unclassified version, which was 190 pages, repeatedly stated that witnesses who were interviewed didn't provide any documents to support the falsification claim.

On whether intelligence was spun to show counter-IS operations in a more positive light, the report was less categorical.

It reported a strong perception among analysts that senior leaders attempted to "distort the intelligence products, either through excessive editing, imposition of a narrative, requiring a higher burden of proof for 'bad news,' or demanding additional sourcing requirements if the intelligence indicated that" IS militants were doing well or that the Iraqi security forces were struggling.

"That widespread perception alone indicated a significant problem," the report said.

One senior analyst told investigators: "Manipulation, watering down, hedging, or preventing from running all together, those are the sort of practices I am talking about."

Another stated: "I wouldn't say falsified, but definitely change and influence."

Their names were withheld.

Senior leaders didn't communicate well with analysts "and they seemed unaware of how their actions and words were perceived," the report said. They didn't explain standards to subordinates and failed to establish trust with many analysts and leaders. The report called for better and more communication between Pentagon leaders and analysts.

Some analysts said intelligence reports weren't massaged.

"It's like an artist," said one analyst. "Every one of these people are artists and they think that their art is perfect the first time, but as it goes up the chain people start asking questions because that's what we're trying to do. We're trying to make these products the best they can be to make them complete."

The report recommended no punishment. Its 29 recommendations included a call for personnel to develop better leadership skills.

Rep. Adam Schiff of California, the House intelligence committee's top Democrat, said the report revealed weaknesses and flaws in the management of the Central Command's intelligence reports.

"CENTCOM still has work to do to bring its intelligence products up to standards, to strengthen dissent channels and to improve morale among its analysts," Schiff said.