Michigan's attorney general is close to announcing charges against three men in the Flint toxic water crisis.

The charges, expected to be announced at a press conference by Attorney General Bill Schuette, will include felonies and will target a Flint city water department employee and two mid-level engineers with the Michigan Department of Environmental Quality, sources have told local ABC affiliate WJRT. At least one of the charges will reportedly relate to falsifying government documents.

The news comes just as a federal judge dismissed a class action lawsuit filed by three Flint residents, ruling that the case is a state matter.

The plaintiffs were seeking $150m (£104m) in damages on behalf of about 31,000 Flint residents. US District Judge John Corbett O'Meara found that the residents had failed to raise any federal issues so he had no jurisdiction in the case.

To save money in April 2014 the city of Flint switched from purchasing treated water from Lake Huron and the Detroit River to treating Flint River water instead.

Unbeknownst to residents, Flint water was far more corrosive and ate away at the water main system causing heavy amounts of lead from the pipes to leach into the water supply. As many as 12,000 children may have been exposed to dangerously high lead levels, risking serious health issues

But the water was toxic in other ways with such a high coliform count that officials at one point recommended boiling before use. Residents also complained of the taste and smell of the water.

Families have been forced to use bottled water for drinking, cooking and even bathing. Michigan Governor Rick Snyder and President Obama declared a state of emergency in Flint in early 2016.

According to some recent tests, the water is now safe to drink as long as it is filtered.

In his State of the State address at the start of the year Snyder apologised to the residents of Flint for his mishandling of the water crisis and vowed to fix the situation. He has been under pressure to resign.