Calling the alleged failure of five New Orleans police detectives to investigate hundreds of reported sex crimes “a disgrace,” Mayor Mitch Landrieu on Tuesday pledged a thorough housecleaning in the NOPD’s sex crimes unit and said a newly formed task force will dig into hundreds of cases that apparently went ignored.

The new task force will be led by 2nd District Cmdr. Paul Noel, who was credited with helping to reform the Special Victims Section — which handles sex crimes — when he oversaw it for eight months in 2010 and 2011.

That’s when the department caught up with a backlog of 800 rape exam kits that had sat unexamined on shelves, while installing new leadership in a bid to change the culture in a unit of eight detectives that has faced repeated criticism over the years.

The results looked promising, with a marked increase in the number of sexual assaults reported by the NOPD, the mayor said. But Landrieu acknowledged that a report last week by Inspector General Ed Quatrevaux’s office makes clear that any changes failed to take hold.

“We now know we did not pull this problem out by the root. I can’t express how angry and frustrated I am by the report,” Landrieu said.

Tuesday’s news conference marked the mayor’s first public statements about a report that has garnered national media attention, revealing an enduring stain on the city’s long-maligned Police Department.

NOPD Superintendent Michael Harrison, weathering the first major black eye for the department in his three months as its chief, acknowledged that he knew the sex crimes unit was troubled well before the revelations from Quatrevaux’s report.

“I was surprised of the magnitude. I was surprised, disappointed and very disturbed by those allegations,” Harrison said. “What we did know was the unit needed some corrective actions.”

Quatrevaux’s office looked at every case from 2011 to 2013 that was assigned to detectives Vernon Haynes, Merrell Merricks, Damita Williams or Derrick Williams, along with Akron Davis, a detective in the Child Abuse Unit. They were singled out as the Inspector General’s Office sampled 90 cases last year for an audit released in May that found dozens of reported rapes had been misclassified.

The report last week found that the five detectives had dumped nearly two thirds of their combined 1,290 cases into the “miscellaneous” bin, leaving no paper trail, while failing to document any follow-up investigation at all into 60 percent of the 450 cases where they had jotted cursory initial reports or notes.

The report cited several examples of the detectives ignoring strong signs a crime had occurred, and it said two of the detectives backdated reports by years in an apparent bid to cover their tracks.

While initially saying all five detectives had been reassigned to patrol duty, the NOPD announced a day later that it had suspended all five detectives pending the outcome of an investigation.

Criminal charges could follow. Their supervisors, too, may have shirked their duties, Harrison said.

“We will look at every single person there is to investigate,” he said.

Noel, who will remain in command of the 2nd District, said the new task force would include four detectives, and more if needed. The unit will investigate 271 cases where Quatrevaux’s office found no supplemental reports written by the five detectives.

The 840 cases that the detectives classified as “miscellaneous” can’t be reviewed because the initial reports from 911 calls are intentionally sketchy, leaving out the victim’s name, for instance. Quatrevaux’s report said there was no way of telling which of them should have been classified as sex crimes.

“I think it’s pretty obvious we had a failure in leadership,” Noel said. “We fixed numerous issues, and there were maybe some issues as well that weren’t completely fixed. There’s no doubt that at this point we will solve everything, and we’ll make rock-solid policies and procedures in the future so this never happens again.”

During most of the period covered in the IG’s report, the Special Victims Section was led by Lt. Louis Gaydosh Jr. He was replaced in September 2013 by Lt. Melvin Gilbert Jr., who retired in May. Harrison placed a new supervisor, Lt. Gervais Allison, in the post in September.

Landrieu declined to say whether former NOPD Superintendent Ronal Serpas dropped the ball on oversight of the sex crimes unit, where Serpas had claimed major progress in engineering a cultural shift to a “victim-centered” approach to investigations.

Landrieu promised to “completely re-create this unit going forward to make sure this never happens again.”

Yet troubles in the unit date back several years, and a 2011 report on the NOPD by the U.S. Department of Justice detailed many of the same problems that Quatrevaux’s office found: numerous cases of poorly documented “miscellaneous” classifications, detectives who seemed to dismiss victims’ claims or ask them accusatory questions, and a routine failure of detectives to interview witnesses and interrogate suspects.

The massive federal consent decree that Landrieu signed more than two years ago, detailing a vast array of court-mandated reforms to the NOPD, described 17 steps the department must take to better handle reports of alleged sexual assaults.

Among them, the decree said, the department must develop “clear policies and procedures” for responding to such reports; create specific guidelines for on-scene and follow-up investigations; follow protocols for examining victims and alleged suspects; and have “direct supervision” of investigators.

The consent decree also required more training for officers and supervisors in responding to reported sexual assaults, and it called for establishing a committee made up of community members to review randomly picked sexual assault probes.

The most recent progress report on those changes came in May, and it wasn’t pretty.

The court-appointed monitor charged with overseeing the NOPD’s reform efforts found nothing to suggest full compliance with any of the 17 requirements. Only in a few instances did the NOPD demonstrate even partial compliance, the report found.

“We’ve actually made great progress in the department over the last two years. But it also points out the reason why we need a consent decree,” Landrieu said Tuesday.

“If you don’t have a sustained management and you don’t change the culture, even individuals who are well-intentioned could turn and do the wrong thing. Which is exactly what happened here,” the mayor said.

Landrieu was flanked Tuesday by Mary Claire Landry, director of the New Orleans Family Justice Center, and Tania Tetlow, a former federal prosecutor who heads Tulane Law School’s Domestic Violence Clinic.

Tetlow expressed confidence in Noel’s ability to turn things around. “There are some really excellent detectives in those units. Something clearly slipped as to the rest of the unit not meeting the newer, higher standards we set four years ago,” she said.

Quatrevaux was on hand for the news conference Tuesday, saying his office would report on the work of the task force in digging through the backlog of cases.

Follow John Simerman on Twitter, @johnsimerman.