Corrections & Clarifications: A previous version of the story had the incorrect date for a community conversation with Solicitor General Fadwa Hammoud.

LANSING, Mich. – The Michigan Attorney General's Office has dismissed all pending criminal charges arising from the Flint drinking water crisis, saying it has instead started over with an expanded investigation.

The office on Thursday announced the dismissal of charges against all eight remaining defendants, including an involuntary manslaughter charge against Nick Lyon, the former director of the Department of Health and Human Services.

Charges were also dismissed against other officials from the health department, plus two former Flint emergency managers and current or former employees of the Michigan Department of Environmental Quality and the City of Flint.

Seven had earlier pleaded no contest to misdemeanors, with expectations they would cooperate with other pending prosecutions and their records would eventually be wiped clean.

Flint residents reacted with shock and confusion.

The statement from the office of Attorney General Dana Nessel said the dismissals were a response to problems with the original investigation, launched under Schuette, and don't preclude recharging the original defendants or adding new ones.

Not all evidence was pursued and Todd Flood, Schuette's special prosecutor, wrongly allowed private law firms representing former Republican Gov. Rick Snyder and other defendants to have "a role in deciding what information would be turned over to law enforcement," according to a joint statement from Solicitor General Fadwa Hammoud, who is handling the criminal cases, and Wayne County Prosecutor Kym Worthy, who is assisting her.

Flood, who was fired by Hammoud on April 14, could not immediately be reached for comment.

In a separate statement, Nessel said she wants Flint residents to know that "justice delayed is not always justice denied," and "a fearless and dedicated team of career prosecutors and investigators are hard at work to ensure those who harmed you are held accountable.”

Nayyirah Shariff, a Flint resident and director of the grassroots group Flint Rising, described the announcement as "a slap in the face to Flint residents," whose residents had their drinking water supply contaminated with lead in 2014, and where many residents still rely on bottled water.

"This has been bungled," she said. "I don't know what's going on."

"I'm very disappointed with Dana Nessel's office because she ran on a platform that she was going to provide justice for Flint residents, and it doesn't seem like justice is coming."

Fifteen people were charged under Schuette, a Republican.

Since 2016, tens of millions of dollars in taxpayers' funds have been spent on the investigation and to pay the criminal defense bills of the state and city defendants.

A "community conversation" is set for June 28 in Flint with Solicitor General Fadwa Hammoud, who is handling the criminal charges, to explain the decision and answer questions.

“Legitimate criminal prosecutions require complete investigations," Hammoud and Wayne County Prosecutor Kym Worthy, who is assisting Hammoud, said in a joint statement.

After taking over the case, "our team of career prosecutors and investigators had immediate and grave concerns about the investigative approach and legal theories" pursued under Flood, "particularly regarding the pursuit of evidence," the statement said.

"After a complete evaluation, our concerns were validated."

The team "worked to salvage whatever progress had been made," but "we were also mindful of the massive expenditure of public resources up to that point and sought to use taxpayer money as efficiently as possible," the statement said.

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But rather than trying to build on "a flawed foundation," prosecutors will dismiss pending charges and "move forward according to the non-negotiable requirements of a thorough, methodical and ethical investigation."

Hammoud asked judges for a six-month pause in the Flint prosecutions in May.

Schuette issued a statement that said his Flint investigation was "staffed and conducted with the highest level of professionalism and expertise," using an "experienced, aggressive and hard-driving team." His statement did not directly address the decision to dismiss the pending charges.

Flood, who was fired by Hammoud on April 14, could not immediately be reached for comment.

Flint resident Melissa Mays, founder of the group Water You Fighting For, said the meeting in Flint, scheduled for late this month, should have been held prior to the announcement or the decision being made. She said she learned about the dismissals from a reporter with The New York Times.

Flood had been moving cases through the court system and meeting with residents, and "I don't understand why scrapping it is the best way to go," Mays said.

"It's extremely terrifying," she said. "Now, we have people who may or may not know what is going on," and "all it does is reinforce that our voices mean nothing."

Nessel, a Democrat who took office Jan. 1, said in a separate statement that she trusts Hammoud and Worthy, and "if this step is necessary for them to do a comprehensive and complete investigation. I am in absolute support."

Nessel said she wants Flint residents to know that "justice delayed is not always justice denied," and "a fearless and dedicated team of career prosecutors and investigators are hard at work to ensure those who harmed you are held accountable.”

After a lengthy preliminary hearing, Lyon was bound over to stand trial on two counts of involuntary manslaughter, willful neglect of duty and misconduct in office. Former Chief Medical Executive Eden Wells was also bound over for trial on involuntary manslaughter and other charges after her preliminary exam in district court in Flint.

Both were accused of failing to act quickly enough on evidence pointing to Flint's drinking water being unsafe to drink.

Lyon’s attorney, Chip Chamberlain, told The Associated Press they “feel fantastic and vindicated.”

Although prosecutors cautioned that Lyon and others could be charged again, Chamberlain said he’s not worried.

“We’re confident that a just and fair investigation, done properly, will yield no evidence of any criminal wrongdoing,” Chamberlain said.

In addition to Lyon and Wells, charges were dismissed against former Flint emergency managers Gerald Ambrose and Darnell Earley, DEQ official Patrick Cook and current or former DHHS officials Nancy Peeler and Robert Scott.

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Mary Chartier, an Okemos attorney representing Scott, said "the dismissal of these charges was the only ethical decision that could be made given that an innocent man was wrongfully accused, charged, and prosecuted."

The statement from Hammoud and Worthy said the team 'has already identified additional individuals of interest and new information," and "these investigative leads will be aggressively pursued."

They said they "understand this decision will not bring immediate remedy or relief to the citizens of Flint, who remain victims of one of the worst man-made environmental disasters in United States history."

However, "we recognize the only acceptable remedy is the vigorous pursuit of justice, which demands an uncompromising investigation ... and professional prosecution of all those criminally culpable."

This month, Hammoud's team executed a search warrant on another part of the Attorney General's Office to seize from storage devices and records related to former Gov. Snyder and dozens of other current or former officials. The warrant sought all contents from Snyder's cellphone, iPad and computer hard drive, fueling speculation that charges against the former governor were still a possibility.

Snyder spoke out against the action, and the way it was reported in the news media, on Twitter, saying he had turned over the devices when he left office and he did not understand why the attorney general's office would execute a search warrant on itself.

Senate Minority Leader Jim Ananich, D-Flint, said he wants "to see people behind bars" over what happened in Flint.

"Words cannot express how disappointed I am that justice continues to be delayed and denied to the people of my city," Ananich said. "Months of investigation have turned into years, and the only thing to show for it is a bunch of lawyers who have gotten rich off the taxpayers’ dime."

Flint's water crisis began in April 2014, when a state-appointed emergency manager switched the city's drinking water supply from Lake Huron water treated in Detroit to Flint River water treated at the Flint Water Treatment Plant. It was a temporary, cost-saving measure, but turned out to be a disastrous mistake. The DEQ has acknowledged it failed to require needed corrosion-control chemicals as part of the water treatment process.

After Flint River water began flowing, corrosive water caused lead to leach from joints, pipes and fixtures, causing a spike in toxic lead levels in the blood of Flint children and other residents.

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Investigators also investigated possible links between the water switch and a spike in Flint-area deaths related to Legionnaires' disease. The manslaughter charges stemmed from some of those deaths.

Flint switched back to Detroit water in October 2015, and tests show water lead levels now within federal limits. But many residents have lost trust in drinking the water, even with filters on their taps, and some risk remains because of possible spikes resulting from ongoing work to replace Flint's lead pipes.

Lonnie Scott, executive director of the liberal group Progress Michigan, said "it’s incredibly disappointing that this investigation was so badly managed by Schuette and his team that it needs a hard reset."

State Rep. Sheldon Neeley, D-Flint, said he hopes the attorney general's office will now join his community in a fight for justice.

"My city is losing faith in our government, and that distrust was justified today when it once again failed them so miserably," Neeley said.

Contributing: The Associated Press

Follow Paul Egan on Twitter @paulegan4.