LANSING, Mich. -- Michigan State has attempted to "stonewall" an investigation into who at the university made mistakes that allowed former doctor Larry Nassar to abuse hundreds of young women, and the school's leaders have been disingenuous in their comments about transparency, according to investigators working with the state's attorney general's office.

An update on the investigation from special counsel Bill Forsyth on Friday morning said Michigan State has issued misleading public statements, drowned investigators in irrelevant documents and waged needless battles over pertinent documents, among other actions that have made it difficult for investigators to determine exactly who knew what about Nassar's serial abuse and what they did about it.

"At some point in time," Forsyth said Friday morning, "just admit you screwed up here and take whatever steps you need to take to rectify it."

Forsyth said he has ended his involvement with the investigation, but that does not mean the investigation has concluded. Other members of the attorney general's staff have roughly 15,000 documents left to review and are still fighting battles in court to force Michigan State to turn over additional documents. This runs counter to interim MSU president John Engler's assertion at a university board meeting last Friday that the investigation had run its course.

Michigan State's board of trustees and Engler asked the attorney general's office to open its investigation last January, days after Nassar was sentenced to up to 175 years in state prison for molesting patients and other girls and young women. Several of the survivors of Nassar's abuse say they told officials at Michigan State, who did nothing to stop him from preying on others.

The attorney general's investigation has thus far led to charges against three former Michigan State employees: former medical school dean William Strampel, former gymnastics coach Kathie Klages and former university president Lou Anna Simon.

Michigan State hired a private law firm to investigate what happened in the Nassar case and to represent the school's interests in the matter long before asking the attorney general's office to do an independent investigation. Those attorneys have told the attorney general's group that they made no formal report about their findings and cannot share information they learned in their investigation because it would violate attorney-client privileges. Forsyth said he believes that at least part of the reason Michigan State hired its own attorneys to do a thorough review was so the university could later withhold that information from outside investigators by claiming it was privileged.

Forsyth said "we may never know" exactly what happened when past reports of Nassar's abuse were disregarded.

Christina Grossi, the investigation's project manager, said her group has asked a local judge to review some of the documents that Michigan State's attorney claim are privileged to determine if they all meet the legal requirements to keep them from the attorney general's investigators. She said her group has found evidence that some high-ranking Michigan State officials included attorneys on email exchanges that weren't intended for them for the sole purpose of shielding investigators from viewing them.

"The concern was MSU employees may have copied attorneys on emails in hopes that it would prevent them from being released," Grossi said.

Grossi said her team interviewed all eight members of the board of trustees and they were "not as forthcoming as we expected them to be." She noted that also included trustees who have publicly called for change and supported survivors.

Forsyth said Michigan State is "trying to have it both ways" by publicly claiming that it is cooperating while fighting the investigators' efforts for transparency. He said many of the more than 500,000 pages of documents Michigan State has provided have been irrelevant material intended to slow down the investigation. For example, he said the school touted the 40,000 pages of documents it turned over at the start of the investigation, but many of those pages were public health policies that explained procedures such as what to do in the case of a tornado and how to reset a password.

"I was fascinated to find out about their bedbug policy," Forsyth said.

Forsyth said his team of investigators interviewed more than 500 people in the past 11 months, including 280 survivors of Nassar's abuse and Nassar himself. Special Agent David Dwyre interviewed Nassar while he was being held in a Michigan jail last February in hopes that Nassar would share information about who else at Michigan State knew about his crimes. Nassar, despite admitting in court that what he did was not for a medical purpose and was for sexual gratification, told Dwyre that what he did was not criminal and was a legitimate medical procedure.

"He was arrogant, I thought, to maintain that his victimization was a legitimate medical practice and he did not take responsibility," Dwyre said. "That's typical of criminals. He was what I'm used to. He was a criminal."

Michigan State spokeswoman Emily Guerrant said the university has "cooperated fully with this investigation." When asked if the school would consider waiving its attorney-client privilege in the interest of increasing transparency, Guerrant said: "Any facts related to Larry Nassar have been handed over to the AG's office, and anything in dispute regarding attorney-client privilege is still being reviewed by an independent third-party judge."

Guerrant did not respond to questions about why Engler said last week that the investigation was over or why the university included apparently irrelevant documents in its responses to the investigation.

Investigators also looked into a claim made this year that Nassar recorded the rape of former Michigan State student-athlete Erika Davis. In a civil lawsuit, Davis claimed that former athletic director George Perles orchestrated a cover-up of the incident. The attorney general's office said it found no credible evidence to support those claims and "in fact, we found substantial evidence contradicting her claims concerning the supposed cover-up."

Forsyth clarified that his group has only investigated claims related to Nassar's abuse at Michigan State. They did not investigate other organizations where Nassar worked or other allegations of mishandled sexual assault claims at the university. He said what they have found was "a failure of people, not policy."

The investigative team's report concluded by saying, "Until there is a top-down cultural change at MSU, survivors and the public would be rightly skeptical of the effectiveness of any set of written policies."