(Reuters) - A group of Flint families with children has filed new lawsuits in the Michigan city’s water crisis, accusing private companies of professional negligence and government employees of misconduct that led to the contamination of the water supply.

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The lawsuits filed on Thursday in Genesee County court, along with nine filed earlier in March, cover 50 children allegedly suffering from lead poisoning from drinking Flint water. The cases were all brought by Corey Stern, a New York attorney who specializes in child lead poisoning cases.

The lawsuits seek monetary damages from engineering firms Lockwood, Andrews & Newnam and Rowe Professional Services Co, two companies involved in carrying out the switch of the city’s water supply from Lake Huron to the Flint River in April 2014.

The more corrosive river water caused lead to leach into the water from the pipes.

Water consultants Veolia North America, which was hired in early 2015 to review Flint’s water quality and found it complied with standards, is also a defendant.

The state’s slow response to the crisis has generated wide criticism and some calls for Michigan Governor Rick Snyder’s resignation.

Flint, a predominantly black city of 100,000, was under the control of a state-appointed emergency manager when it switched its water source for cost reasons. It was switched back last October after tests found high levels of lead in blood samples taken from children.

Stern said the varying effects of lead poisoning on children makes individual lawsuits more appropriate than class actions. He expects to file lawsuits covering 25 more children next week.

Even small amounts of lead can cause permanent damage, particularly in children.

A Lockwood Andrews representative said the firm’s work addressed specific components of the water treatment plant, not the overall water quality.

Veolia said it was hired by Flint to study the residual impact of the city’s chlorination process and stands by its work. The city conducted lead tests through another company, Veolia said.

The lawsuits brought by Stern also accuse two state employees and a city employee of gross negligence.

A separate federal class action filed on Monday seeks damages on behalf of a proposed class of “tens of thousands” of Flint residents and property owners, claiming Snyder and other governmental officials failed to eliminate the dangers as federal law required and downplayed the severity of the contamination.

Other lawsuits seek compensation for water bills, immediate replacement of lead pipes or injuries to residents.