New Orleans residents who lived through hurricane Katrina remain grateful for NBC News anchor Brian Williams’ reporting from the city during and after the storm.

They just have doubts about some of it.

Williams’ past reporting has come under new scrutiny after revelations earlier this week that he had peddled a false story about what he described as a near-death experience in which a US army helicopter he was riding in in Iraq in 2003 came under RPG and AK-47 fire. The story was exposed by US soldiers as false. Williams called it a “mistake” and apologized.

Longtime residents of New Orleans’ French Quarter say they believe Williams’ vivid claims about his Katrina reporting in the years since the devastating August 2005 storm have also been overblown. They shake their heads at Williams’ having said that he saw a body floating face-down outside his hotel. They say it is highly unlikely that Williams’ hotel was “overrun with gangs”, as the anchor has said. They say there was no dysentery, a disease Williams has said that he caught while he was in the city reporting, and that bottled water was plentiful in the area – despite Williams’ claims to the contrary.

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“I saw one of his tapes last night. He said he was told not to drink bottled water in front of people because people would kill you for it?” said Dr Brobson Lutz, a former director of the New Orleans city health department who is a longtime resident of the French Quarter and who ran an EMS station there after the storm. “That’s absolutely hogwash.”

Detailed doubts about Williams’ recollections of Katrina were raised in a New Orleans Advocate story on Friday. Two of Williams’ claims about Katrina explored by the Guardian, of seeing a floating body from his hotel and encountering threatening gangs, while attracting the deep skepticism of locals, were difficult to verify because it was unclear which hotel or hotels Williams stayed in. The Advocate later published a second report that documented flooding around the Ritz-Carlton, one hotel where Williams is believed to have stayed, and acknowledged that “a number of bodies were recovered in that general area”.

NBC News did not respond to several messages left seeking comment on Friday. Network president Deborah Turness, a former ITV executive, said in a memo to staff that an internal investigation was under way. “This has been a difficult few days for all of us at NBC News,” Turness said.

One of Williams’ most vivid descriptions from his time in New Orleans was of seeing a man “float by face down” from his “hotel room window in the French Quarter”. He described the experience in a 2006 interview with Michael Eisner, who had just stepped down as CEO of Disney, the parent company of ABC News. “I felt something get dislodged that changes the usual arms-length relationship between me and the stories I cover,” Williams said. “These are Americans. These are my brothers and sisters. And one of them was floating by.”

Locals remember NBC crews staying in the Ritz-Carlton or Windsor Court or both.

An archived United Methodist News report with pictures said to be taken by a minister from the Ritz-Carlton hotel during Katrina documents water deep enough to float a boat and, presumably, a body. An interactive graphic of flooding during Katrina produced by the New Orleans Times-Picayune depicts the edge of flooding from the storm as having crept into the northern section of the French Quarter. A photograph from the time near the corner of Dauphine and Canal, where the Ritz-Carlton is located (map), shows shin-deep water. Darren Crumpton, director of sales and marketing at the Ritz-Carlton, said the hotel does not provide the names of past or future guests, and said the hotel would not take questions about water outside the property during Katrina.

“I seriously doubt it,” said a longtime resident of North Rampart Street in the quarter, Leo Watermeier, a community activist. “I was around there. There was no bodies. There was no major flooding downtown. The water at most was a foot deep. Nobody had drowned around there. So I would be skeptical of that, myself.”

“There were – most of the Quarter, I would say 95% of the quarter didn’t even get any floodwater,” said Lutz. “While there are some pictures of bodies floating around in parts of the more flooded areas of the city, there weren’t any bodies floating around the Quarter.”

Public perception of the aftermath of the hurricane has been heavily informed by pictures of devastation in the city and news reports at the time of widespread violence that turned out later to be unfounded. Pictures of bodies floating in the water have been widely distributed, but they were not a common sight at the time, said Dr John Kokemor, who worked in the aftermath of the storm at Memorial Baptist hospital in the Broodmoor neighborhood.

“I was over here and we had eight feet of water. I didn’t see any floating bodies. Zero,” said Kokemor. “We’re in the lowest part of town; we’re at the bottom of the bowl. On that side of the street we had eight feet. On the opposite side of the street we had seven feet. Suffice it to say, the water here was quite high, and I didn’t see any bodies.”

Williams and NBC News have been accused before of exaggerating violence in the city after the storm. The nonprofit Fairness and Accuracy in Reporting took issue with a 2010 Katrina anniversary report in which Williams said: “State troopers had to cover us by aiming at the men in the street just to tell them, ‘Don’t think of doing a smash and grab and killing this guy for the car.’” Fair pointed to a September 2005 Times-Picayune report that found that “the vast majority of reported atrocities committed by evacuees – mass murders, rapes and beatings – have turned out to be false, or at least unsupported by any evidence, according to key military, law-enforcement, medical and civilian officials in positions to know.” A report published in the American Journalism Review in January 2006 found that “the impressive media coverage of Hurricane Katrina was marred by the widespread reporting – sometimes attributed to public officials – of murders and rapes that apparently never took place.”

Watermeier contradicted Williams’ description of roving gangs in the area after the storm. “Our hotel was overrun with gangs,” Williams told his predecessor, Tom Brokaw, in an interview last year.

Not true, said Watermeier. “People were afraid that was the case,” he said. “I don’t think that really was the situation. Once darkness came, that was frightening. Just because it was pitch-black. And you felt vulnerable. The looting was being done pretty much in the open. And it wasn’t just looting for survival. It was looting, people taking advantage of the situation.

“There was no law around. And you felt that vulnerability. But I didn’t see anything.”

Lutz, who is now in private practice, set up an emergency medical station near his home and ran it most days for a month after Katrina. He questioned Williams’ description of having “accidentally ingested some of the floodwater” and becoming “very sick with dysentery”.

“The floodwaters, in order to get dysentery, you have to drink water that’s been contaminated with human sewage. That’s what happens when you go to a hotel in Mexico,” Lutz said.

“The water that came from Lake Ponchartrain and all that, it was mucky, it was nasty-looking and all, but people didn’t go around drinking it. He said he mistakenly drank some of it, or somehow drank some of it – you’d have to be a fool to drink that water.

“The biggest medical problems that we saw were cuts and scrapes and bruises, and then skin and soft tissue infections, you know secondary infections from people scraping themselves.”

A 2005 study by the Centers for Disease Control and Prevention of disease in evacuees and rescue workers after Katrina documented reports of “clusters of diarrheal disease among persons in evacuation centers” but no dysentery cases. “No confirmed cases of Shigella dysentery, typhoid fever, or infection by toxigenic V cholerae O1 were reported in evacuees from Hurricane Katrina,” the CDC report said. According to a National Institutes of Health report, New Orleans health officials acting on concerns of an E coli outbreak tracked “cases of watery and bloody diarrhea” after the storm and found they had occurred in as many as 10% of documented patients.

Dysentery, an inflammation of the intestines, has symptoms that could be confused with other forms of gastroenteritis, including diarrhea. According to the New Orleans Advocate, shortly after the storm CNN interviewed a guest at the Ritz-Carlton who said that doctors who’d set up a makeshift clinic had treated what they apparently believed to be dysentery.

At least 80% of the Gulf Coast city, much of which lies below sea level, saw flooding from the storm and subsequent levee breaches. At least 971 died in Louisiana from the storm, and an equal number died in other coastal states, according to health officials.

New Orleans residents remain grateful to Williams for his reporting on the storm and its aftermath. Williams spent two weeks in the city and won, with NBC News, an Alfred I duPont-Columbia University Award for the work.

“I think people here were very appreciative,” Watermeier said. “We felt like he had been through this. It was a really life-changing experience for everybody who went through Katrina.

“There was a sense that he had been here with us. He experienced it, was very sympathetic, kept coming back. He was very supportive and people really appreciated everything he tried to do to try to get the word out about what was happening.”