Michigan filed the first criminal charges Wednesday in the scandal over lead contamination of Flint's water supply, accusing a city official and two state regulators of falsifying tests and tampering with evidence.

State attorney general Bill Schuette said the three knowingly misled local, state and federal officials about lead levels in the water supply of Flint, an economically depressed majority black city of 100,000 where people have resorted to using bottled water.

More than 8,000 children are believed to have drunk the tainted city water -- which unbeknownst to the public had soaring lead levels for months before it was discovered -- triggering fears about a sickened generation in Flint.

"So many things went so terribly wrong and tragically wrong in Flint," Schuette said in announcing felony and misdemeanor charges against state regulators Stephen Busch and Michael Prysby and Flint utilities administrator Michael Glasgow.

The charges, which carry up to five years in prison, were the first produced by the state and federal probes launched after the high lead levels were disclosed by citizen activists in October.

The tainted water stemmed from a decision to shift Flint's water source from the Detroit River to the Flint River as part of cost-cutting measures ordered by state Governor Rick Snyder, a Republican who has consistently resisted calls to quit.

Experts believe the chemical-laced Flint River water corroded lead pipes, allowing large amounts of the chemical element to leach into the city's water.

Todd Flood, the special assistant attorney general who is investigating, warned that more charges were likely.

"We will turn over every stone. We'll go down every rabbit hole. This is just the first wave," he said.

Flint Mayor Karen Weaver said it was time "to stop the finger-pointing between the state and federal government" and get the city help.

"We haven't been able to drink our water. We haven't been able to cook with it and bathe with it," she said.

"You start thinking: are we not American citizens? Aren't we worth this?"

- 'Altered test results' -

Experts say it will take years to replace the corroded water pipes in Flint, which has been blighted by high crime and a dwindling population since its auto industry collapsed from the late 1980s onwards -- a far cry from its heyday as the home of General Motors.

Snyder said "people deserved the truth," but denied wrongdoing.

"I have not been questioned or been interviewed at this point in time," he told a press conference. "People deserve the answers. They want accountable government and they should get it."

"If these accusations (against the three) are correct, this will take it to a whole new level," he added.

Schuette accused the two state regulators of "intentionally tampering with evidence of lead levels on certain water samples in homes of residents of Flint."

"We allege and we'll prove that Mr Busch and Mr Prysby altered test results, which endangered the health of families and citizens of flint," he said.

Prysby received an additional felony charge of authorizing the operation of the Flint water treatment center "knowing that the plant would fail to provide clean and safe drinking water to families of Flint."

"They had a duty to protect the health of families and citizens of Flint. They failed, they failed to discharge their duties," he said.

Glasgow, a supervisor at the Flint water treatment plant, was charged with "felony tampering with evidence by falsifying and altering reports" to the state's Department of Environmental Quality and the federal Environmental Protection Agency.

He also received a misdemeanor charge of "willful neglect of duty."