(This story corrects Esposito's position at the Daily News in 8th paragraph)
By Patricia Reaney
NEW YORK (Reuters) - NBC launched an internal probe on Friday into top-rated "Nightly News" anchor Brian Williams' debunked claim that he was aboard a helicopter that was downed by a rocket-propelled grenade (RPG) during the U.S. invasion of Iraq in 2003.
In an internal memo, NBC News President Deborah Turness told staffers that a team would gather the facts about the incident in which Williams, 55, falsely said he was in a U.S. Army helicopter that was hit and forced down by an RPG.
"This has been a difficult few days for all of us at NBC News," she said. "As you would expect, we have a team dedicated to gathering the facts to help us make sense of all that has transpired."
Williams apologized on TV on Wednesday for "making a mistake" after veterans complained about the claim he made during a broadcast last week, saying it was not true.
But the lie threatens his credibility as the anchor and managing editor of NBC's flagship evening news program.
“I was instead in a following aircraft. We all landed after the ground fire incident and spent two harrowing nights in a sandstorm in the Iraq desert,” Williams said in his apology.
He blamed it on repeatedly watching a video of himself looking at the impact damage and "the fog of memory over 12 years" that he said made him misremember.
The probe by the network's investigative unit is being headed by Richard Esposito, who was formerly an editor at the Daily News newspaper of New York, according to media reports.
The apology by Williams did little to quell the uproar and cast doubt about whether he would be able to continue in his role at NBC, a unit of Comcast Corp.
"We're working on what the best next steps are," Turness added in the memo.
NBC did not respond to requests for comment, and Williams appeared on his evening news show on Friday.
But the Emmy-winning anchor was ridiculed on social media and in the press for his "lame apology."
"Now Williams is under fire," read a banner headline in the New York Post, which listed other interviews and news segments in which he spoke about his helicopter being forced down.
Williams is also facing scrutiny about his remarks about covering Hurricane Katrina. In an interview he spoke about seeing a deceased man float face down from his hotel window in the French Quarter of New Orleans.
But a former city health director, Dr. Brobson Lutz, told the New Orleans Advocate he questioned Williams' account because the historic district did not experience as much flooding as other parts of the city.
Lutz was also dubious about comments Williams made in another interview when he said he suffered from dysentery after mistakenly drinking flood water while covering Katrina.
"I saw a lot of people with cuts and bruises and such, but I don't recall a single, solitary case of gastroenteritis during Katrina or the whole month afterwards," said Lutz.
(Reporting by Patricia Reaney; Editing by Eric Kelsey, Christian Plumb and Lisa Shumaker)