By Steve Friess

FLINT, Mich. (Reuters) – Michigan prosecutors on Tuesday charged four former government officials with criminal conspiracy to violate safety rules in connection with the Flint water crisis, which exposed residents to dangerous levels of lead, the state’s attorney general said.

Former state-appointed emergency managers Darnell Earley and Gerald Ambrose and former city employees Howard Croft, a public works superintendent, and Daugherty Johnson, a utilities manager, were the latest to be charged in the case, Attorney General Bill Schuette said.

He told a news conference in Flint that the defendants conspired to operate the city’s water treatment plant when it was not safe to do so.

“The tragedy that we know of as the Flint water crisis did not occur by accident,” Schuette said. “Flint was a casualty of arrogance, disdain and failure of management, an absence of accountability.”

Asked whether the investigation would lead to charges against higher-placed state officials, Schuette reiterated that no one was off the table.

Some critics have called for high-ranking state officials, including Michigan Governor Rick Snyder, to be charged. Snyder has said he believed he had not done anything criminally wrong.

Court documents did not list attorneys for the four men. An attorney who had previously represented Earley could not immediately be reached for comment.

Michigan has been at the center of a public health crisis since last year, when tests found high amounts of lead in blood samples taken from children in Flint, a predominantly black city of about 100,000.

Flint’s water contamination was linked to an April 2014 decision by a state-appointed emergency manager to switch the city’s water source to the Flint River from Lake Huron in an attempt to cut costs.

The more corrosive river water caused lead to leach from city pipes into the drinking water. The city switched back to the previous water system in October 2015.

The initial change in the city’s water source was made while Earley, 65, was emergency manager.

At hearings in Washington last March on the crisis, lawmakers criticized Earley for failing to ask enough questions about the safety protocols in place at the time of the switch. In his testimony, Earley blamed city and federal officials for the problems, and said the decision to switch was made before his tenure.

“A broad net is certainly being cast,” said Virginia Tech professor Marc Edwards, a water engineer who first raised the issue of Flint’s lead contamination.

Lead can be toxic, and children are especially vulnerable. The crisis has prompted lawsuits by parents who say their children have shown dangerously high levels of lead in their blood.

(Additional reporting by Laila Kearney in New York and Timothy McLaughlin in Chicago.; Editing by Dan Grebler)