DETROIT (CBS DETROIT/ AP) — All criminal charges against eight people in the Flint water scandal were dropped Thursday.

Prosecutors have pledged to start the investigation from scratch.

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Michigan Solicitor General Fadwa Hammoud said “all available evidence was not pursued” by the previous team of prosecutors. Hammoud took control of the investigation in January after the election of a new attorney general.

The defendants included Michigan’s former health director, Nick Lyon, who was charged with involuntary manslaughter.

In 2014-15 when Flint was drawing improperly treated water from the Flint River, Lyon was accused of failing to alert the public in a timely manner about an outbreak of Legionnaires’ disease. This led to residents’ water being tainted with lead. The uproar over water quality reached a peak by fall 2015 when a doctor reported high levels of lead in children, which can cause brain damage.

Prosecutors said it is possible that Lyon and others could be charged again.

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The investigation began three years ago but no one is behind bars. Seven of 15 defendants have pleaded no contest to misdemeanors. Their records will eventually be scrubbed clean.

Charges were pending against eight people, including former Michigan chief medical executive Eden Wells and two men who were state-appointed emergency managers in Flint.

Flint was being run by financial managers appointed by the governor due to poor finances.

The city’s water no longer comes from the river and has significantly improved, but some residents do not trust the water quality that they have continue to use bottled water.

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