Researchers at Virginia Tech who looked into the lead poisoning were even more damning, reporting last month that Michigan officials not only ignored complaints about the smell, taste and color of the water, but also lied about lead levels and tried to conceal evidence. And there have been reports that the city failed in its own lead-testing duties.

The state says it has identified 43 people suffering from elevated levels of lead, which poisons the nervous system and can stunt brain development in children. In addition, state officials disclosed this week that in 2014 and 2015, there was a spike in Legionnaire’s disease cases in Genesee County, which includes Flint, including 10 fatalities, coinciding with the contamination of the water supply. They said they were investigating whether there might be a connection.

From 2011 to 2015, Flint was in state receivership, its finances controlled by a succession of four emergency managers appointed by Mr. Snyder’s administration. The state returned some financial control to the city last year, and Mr. Snyder said Friday that he wanted to give it still more autonomy.

It was one of those state-appointed managers who, in a cost-cutting move, switched the city in April 2014 from taking water from Detroit’s system to drawing water from the Flint River.

Almost immediately, people began to complain about the water’s color, smell and taste. Bacterial contamination was found, and then the chemicals used to disinfect the water caused a different kind of contamination, but state officials insisted that the problems had been managed and that the water was safe.

It was not until September that evidence of lead poisoning became public, and officials began to acknowledge it. It turned out that the river water was corrosive, causing lead to leach from pipes.