US President Barack Obama next to Gen. Lloyd Austin III, the commander of Central Command, during a briefing from top military leaders while at MacDill Air Force Base in Tampa, Florida, in 2014. REUTERS/Larry Downing Top US military officials used subtle manipulation tactics to influence the outcome of intelligence reports on the fight against ISIS in the Middle East, according to analysts who detailed specific allegations from the growing scandal to NPR.

Unnamed military sources told NPR that leaders at US Central Command, or Centcom, had tougher standards for reports involving bad news and changed the wording of reports to make them sound less negative.

When analysts wanted to include good news in a report, two military sources close to the investigation said, they needed little sourcing. Bad news, meanwhile, required extensive footnotes and intelligence data to back it up.

"The bad news didn't just need to be footnoted," one military source told NPR. "The intelligence data itself had to be attached to the report."

"It became pretty clear if they wrote something bad, it was likely to be changed," the source added. "Knowing that bad news on ISIS wasn't welcome meant that, over time, the picture of the fight began being rosier."

The Pentagon is investigating accusations that top military officials pressured analysts into conforming their reports to a more positive narrative of the fight against the militant group ISIS (also known as the Islamic State).

More than 50 intelligence analysts at Centcom, the Pentagon agency covering security interests in nations throughout the Middle East and Central Asia, have supported a formal complaint sent to the Defense Department that accuses senior intelligence officers of insisting on changing ISIS reports to make them reflect more positively on US efforts in the region, The Daily Beast reported last week.

Language was also sanitized, according to the NPR report.

A source described one report about an ISIS attack near the Iraq/Syria border. According to the source, the report initially said Iraqi security forces "retreated," meaning they fled their positions, but it was then sent back for editing and later came to say that the soldiers reinforced another Iraqi position.

"The final draft suggested a strategic decision had been made," Dina Temple-Raston wrote for NPR. "But that was not what happened, the source said — the Iraqi forces ran. A second source confirmed the account of the change in wording to put the Iraqi forces in a more positive light."

Sources previously told The Daily Beast that senior military and intelligence officials also pushed analysts to portray ISIS "as weaker than the analysts believe it actually is."

The concern is that the pressure from military officials, if true, may spring from a desire to align ISIS intelligence reports with what the Obama administration has been saying about the fight against the extremists. Sources told The Guardian that administration officials were not open to "the narrative that ISIS is winning."

Centcom analysts are now in a full "revolt," according to The Daily Beast. The work environment there has reportedly gotten so bad that it has been described as "Stalinist." One source said that when analysts brought concerns to Centcom leadership, they were urged to retire, and some agreed to leave.

Gen. Lloyd Austin, the head of Centcom, testified before the Senate Armed Services Committee this week to update members on the US-led fight against ISIS. He was asked to address the allegations surrounding manipulated intelligence reports and said "it would be premature and inappropriate for me to discuss this matter" because of the ongoing investigation.

Austin did point out, however, that Centcom reports did not go directly to the president and that Centcom had a wide variety of sources that provide its intelligence analysis, according to NPR.

A Centcom spokesman told Business Insider last week that it welcomed the Pentagon inspector general's investigation.

"The IG has a responsibility to investigate all allegations made, and we welcome and support their independent oversight," the spokesman said. "While we cannot comment on the specific investigation cited in the article, we can speak to the process. The Intelligence Community routinely provides a wide range of subjective assessments related to the current security environment.

"These products and the analysis that they present are absolutely vital to our efforts, particularly given the incredibly complex nature of the multifront fights that are ongoing now in Iraq and Syria. Senior civilian and military leadership consider these assessments during planning and decision-making, along with information gained from various other sources, to include the insights provided by commanders on the ground and other key advisors, intelligence collection assets, and previous experience. The multisource nature of the assessment process purposely guards against any single report or opinion unduly influencing leaders and decision-makers."