(CNN) Nearly four years since the city of Flint declared a state of emergency over the state of its water -- and three years after the first criminal charges were filed against government officials -- prosecutors on Thursday dismissed all pending criminal cases, pledging to start the investigation from scratch.

Prosecutors said that they had grave concerns about the investigative approach and legal theories embraced by the former Office of Special Counsel (OSC) that oversaw the investigation, according to a press release issued by the Michigan Department of Attorney General. The OSC was appointed by former Attorney General Bill Schuette.

The OSC entered into agreements that gave private law firms that were representing the accused a role in deciding what information would be turned over to law enforcement, according to the release.

"We cannot provide the citizens of Flint the investigation they rightly deserve by continuing to build on a flawed foundation," said Solicitor General Fadwa Hammoud and Wayne County Prosecutor Kym L. Worthy, who are now leading the criminal cases.

Prosecutors noted in the press release that "the voluntary dismissal is not a determination of any defendant's criminal responsibility." Prosecutors are not precluded from refiling charges against the defendants in the future.

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