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Michigan's top prosecutor launched an investigation Friday into the Flint water crisis to see if any laws were broken — as the local sheriff declared that “people lied to us.”

“In 21st century America, no one should have to fear something as basic as turning on the kitchen faucet," Attorney General Bill Schuette said in a statement.

"I look forward to working with federal, state and local officials, community leaders and Flint residents as we seek answers regarding state law and hope through the process we can help restore some of the trust in our government while helping families move forward."

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Federal prosecutors are already probing the debacle that has exposed nearly everyone in the city of 99,000 to lead poisoning and other contaminants. The state Health Department has just started investigating whether an increase of Legionnaires' disease cases — seven of them fatal — could be linked to the crisis.

"We are hopeful the culpable parties will receive justice," said Gerald Kariem of the United Auto Workers, which was handing out bottled water and filters on Friday.

The crisis dates back to April 2014 when Flint switched water sources to save money. The new supply, from the Flint River, was saltier and corroded pipes, leaching lead into the system.

A buildup of lead in the body can cause mental and physical problems, or even death, and small children are especially vulnerable. Experts say there is no safe level of lead.

As NBC has reported, an aide to Gov. Rick Snyder wrote in an email — which was obtained by researchers as Virginia Tech — that he feared the state was "blowing off" the worried citizens of Flint in July, six months before a state of emergency was finally declared.

Another email from the summer shows that a state epidemiologist identified a spike in lead levels in Flint and warned that more investigation was needed, but no one acted. Michigan's chief medical officer told NBC News the email was a "missed opportunity."

Snyder, who has been under fire for his handling of the situation, has asked President Obama to declare a major disaster in Flint. The Federal Emergency Management Agency said the request is under review and will be considered "expeditiously."

Friday's announcement to open a probe into the water crisis comes less than a month after Schuette reportedly declined to investigate officials' response to the problem, according to documents published by NBC affiliate WEYI Friday.

A state representative, Sheldon Neeley, in September asked Schuette to investigate whether Flint of the state have "culpability and responsibility" for the problem, but Schuette's office declined in December, citing multiple reviews by other agencies and pending federal court action, the documents said.