NEW YORK (Tribune Content Agency) — Brian Williams’ false statements regarding his experience on a military helicopter during the 2003 invasion of Iraq have turned into a full-blown crisis.

NBC News has launched an internal investigation into the anchor’s accounts of his travels in Iraq, which have come under attack from Iraq War veterans and are spurring a growing chorus from media critics who say his journalistic credibility has been seriously undermined. Williams has said in recent years that he was in a Chinook helicopter that was brought down by grenade and small arms fire, even though his original 2003 reporting said it was another helicopter in the convoy that was hit.

NBC News President Deborah Turness said an internal investigation is underway.

“We have a team dedicated to gathering the facts to help us make sense of all that has happened,” she said in a statement. An NBC News executive who was not authorized to speak publicly told the Los Angeles Times that Richard Esposito — the head of the news division investigations unit — is overseeing the inquiry.

An NBC investigative reporter called Stars and Stripes reporter Travis Tritten on Friday. Tritten was first to report that there were questions about Williams' account of what happened in 2003.

The controversy has now extended to Williams’ reporting in New Orleans in the aftermath of Hurricane Katrina in 2006. The executive also said possible contradictions that have surfaced in that coverage will be examined as well.

If the investigation demonstrates a pattern of Williams straying from the facts, the anchor’s status could be in jeopardy. NBC News executives are discussing possible scenarios if Williams has to take a leave of absence or resign from “NBC Nightly News,” the executive told the Times.

Williams, who perpetuated the erroneous version of the Iraq incident on “NBC Nightly News” and in a 2013 interview on “The Late Show with David Letterman,” apologized for the mistake on the air Wednesday, and again before news division staffers on Friday afternoon. But his statements have failed to alleviate the criticism and comments from members of the crew on the helicopter that was attacked that day who contradict Williams’ account.

One pilot who verified parts of Williams’ story to CNN on Thursday has recanted his story, saying his memory of the events is unclear.

The pilot, Richard Krell, told CNN in an interview Thursday that he was flying the helicopter that Williams was on in Iraq in 2003 — a helicopter the anchor initially claimed was forced down by enemy fire. Krell contradicted Williams’ claims about being aboard the helicopter that was forced down, but said Williams had been there during the time of the attack.

Krell said the three helicopters in the formation, which included the one Williams was on, came under “small arms fire.”

But on Friday morning, in a text to CNN reporter Brian Stelter, Krell seemed to question his own account after other helicopter pilots told The New York Times that they had piloted Williams’ helicopter and did not recall their convoy coming under fire.

“ … the information I gave you was true based on my memories, but at this point I am questioning my memories,” Krell said, according to CNN.

Stars and Stripes and Times staff writer Brittny Mejia contributed to this report.

©2015 Los Angeles Times. Distributed by Tribune Content Agency, LLC.

