The Environmental Protection Agency’s top Midwest official is resigning over the Flint water crisis, the agency announced Thursday, amid criticism over the agency’s alleged inaction in preventing the city’s water from being contaminated with lead.

Region 5 administrator Susan Hedman offered her resignation and will leave in February after it was accepted by Administrator Gina McCarthy, the EPA said in a statement.

Hedman, the EPA’s top Midwest official, had previously told The Detroit News the agency knew about the lack of corrosion control in the water supply as early as April, after an EPA official identified problems with the drinking water, but did not make the information public.

The resignation comes just two days after the EPA admitted its response to the crisis was too slow.

"Our first priority is to make sure the water in Flint is safe, but we also must look at what the agency could have done differently," the agency said in a statement Tuesday. An EPA spokeswoman confirmed the agency believed it did not act fast enough to address the problem, according to Reuters.

The EPA said that McCarthy sent Michigan Gov. Rick Snyder a letter issing a Safe Drinking Water Act Emergency Order, which requires the city and state of Michigan to take a series of "immediate steps" to address the drinking water contamination in Flint.

"EPA has determined the State of Michigan and the City of Flint’s responses to the drinking water crisis in Flint have been inadequate to protect public health, there are serious, ongoing concerns with delays, lack of adequate transparency, and capacity to safely manage the drinking water system," the agency said in a statement.

Flint's water became contaminated with lead when the city switched its water source in 2014 as a cost-cutting measure while the city was under state financial management. The Flint River water was not properly treated to keep lead from pipes from leaching into the supply. Elevated blood-lead levels were found in two city zip codes.

The community about 75 miles north of Detroit, has about 100,000 residents, with about 40 percent of them living below the poverty line. The population is nearly 60 percent black.

Republican Governor Rick Snyder, who has faced fierce criticism for his role in the crisis, apologized in December and Michigan's top environmental regulator, Dan Wyant, resigned after a task force created by Snyder blamed problems on his agency.

The group said the Department of Environmental Quality erred by not requiring Flint to keep corrosive water from leaching lead from service pipes into residents' homes and belittling concerns from the public. 

The lead — which can lead to behavior problems and learning disabilities in children and kidney ailments in adults — has left Flint residents unable to drink unfiltered tap water. The National Guard, state employees, local authorities and volunteers have been distributing lead tests, filters and bottled water. Snyder aides pledged that by the end of the week, officials would visit every household in Flint to ensure they have water filters.

President Obama, meanwhile, designated Flint a federal emergency on Saturday but has refused Snyder’s request to designate it a disaster zone as it is a man-made incident.

Flint Mayor Karen Weaver refused to call for Snyder's resignation while at a U.S. Conference of Mayors meeting in Washington, D.C., saying investigations should go forward. She said she wants Snyder to give Flint the services and the money needed to address the problem.

"People have said how they want things handled with him," Weaver said Wednesday. "I'm staying focused on what I need to get from him right now."

The U.S. Justice Department is helping the Environmental Protection Agency to investigate, and GOP state Attorney General Bill Schuette has opened his own probe.

The agency said that McCarthy has sent a memo to all staff instating a formal policy, effective immediately, on elevation of critical public health issues, while also requesting the EPA's Office of Inspector General conduct an evaluation of the region's public water system supervision program under the Safe Drinking Water Act.

The Associated Press contributed to this report.