Michigan Civil Rights Commission has blamed decades of ‘systemic racism’ for water crisis in the impoverished US city.

Five people, including the head of Michigan’s health department, were charged with involuntary manslaughter in an investigation of the beleaguered US city of Flint’s lead-contaminated water, all blamed in the death of an 85-year-old man who had Legionnaires’ disease.

Nick Lyon is the highest-ranking member of Republican Governor Rick Snyder’s administration to be snagged in a criminal investigation of how the city’s water system became poisoned after officials tapped the Flint River in 2014.

Lyon, 48, the director of the Health and Human Services Department, is accused of failing to alert the majority-black population about an outbreak of Legionnaires’ disease in the Flint area, which has been linked by some experts to poor water quality in 2014.

An involuntary manslaughter conviction carries up to 15 years in prison.

“The health crisis in Flint has created a trust crisis for Michigan government, exposing a serious lack of confidence in leaders who accept responsibility and solve problems,” said state Attorney-General Bill Schuette on Wednesday.

The Michigan Civil Rights Commission issued a report in February blaming “systemic racism” going back decades for the problems that caused the water crisis in Flint.

READ MORE: State of emergency in US city after water poisoned

Flint began using water from the Flint River while under state emergency management, but did not treat it to reduce corrosion. Toxic lead from old plumbing leached into the water system, causing elevated levels in children and leaving residents to drink and bathe with bottled or filtered water.

Some experts also have linked the water to Legionnaires’ disease, a type of pneumonia caused by bacteria that thrive in warm water and infect the lungs. People can get sick if they inhale mist or vapor, typically from cooling systems.

There were nearly 100 cases in the Flint area, including 12 deaths, in 2014 and 2015.

Schuette said his probe is moving to the trial phase and signaled that Governor Snyder, who has apologised for his administration’s failures that led to and prolonged the crisis, may not be charged.

“We only file criminal charges when evidence of probable cause of a crime has been established. And we’re not filing charges at this time,” he said.

Lyon also is charged with misconduct in office for allegedly obstructing university researchers who are studying if the surge in cases was linked to the Flint River.

The others charged with involuntary manslaughter were already facing other charges. They are: Darnell Earley, who was Flint’s emergency manager when the city used the river; Howard Croft, who ran Flint’s public works department; Liane Shekter Smith; and Stephen Busch. Shekter Smith and Busch were state environmental regulators.

Prosecutors also brought charges Wednesday against a sixth person— the state’s chief medical officer, Dr Eden Wells, 54, who is accused of obstruction of justice and lying to an investigator.

“Dr Wells vehemently denies the charges,” defense attorney Jerry Lax said.

Shekter Smith’s lawyer, Brian Morley, said: “It’s my understanding neither she nor the Department of Environmental Quality were responsible for legionella issues. So I fail to see why the charge is being filed against Liane.”

Earley’s attorney Todd Perkins said he’s “very disappointed in these new charges,” adding his client has “done nothing wrong.”

Chip Chamberlain and Larry Willey are representing Lyon and called the charges “baseless.”

“The true facts simply do not support the prosecution’s claims,” they said in a statement.

READ MORE: Flint: The US city where people drank poisoned water

Convincing a jury that the officials’ failure to disclose the risk of Legionnaires’ disease caused a death would be difficult, Wayne State University law professor Peter Henning said.

“This case is going to become a battle of the experts, something we don’t usually see in a homicide or manslaughter prosecution,” Henning said. “This is a tough case for the attorney general. They can get a conviction but it’s not going to be easy.”

Lyon, Croft, Earley, Shekter Smith and Busch are blamed in the death of Robert Skidmore in December 2015. He was admitted to McClaren Flint hospital in June 2015 with symptoms consistent with pneumonia. He died at home six months later.

Lyon was personally briefed in January 2015 but “took no action to alert the public of a deadly” outbreak until nearly a year later, special agent Jeff Seipenko told a judge as the charges were filed.

Schuette has now charged 15 current or former government officials in an ongoing probe that began in early 2016, including two emergency managers whom Snyder appointed to run the impoverished city of roughly 100,000 residents.