The Environmental Protection Agency official who oversaw the Midwest region resigned Thursday evening over the contaminated drinking water crisis in Flint, Mich.

"EPA Region 5 Administrator Susan Hedman has offered her resignation effective February 1, and EPA Administrator Gina McCarthy has accepted given Susan's strong interest in ensuring that EPA Region 5's focus remains solely on the restoration of Flint's drinking water," the EPA said in a statement released Thursday, reported The Associated Press.

In an effort to save money, Flint switched water supplies to the Flint River in April 2014, but the more corrosive river water was not treated properly and caused lead to leach out from the city's aging pipes. Elevated levels of lead, a potent neurotoxin that can damage the brain, were found in the blood of people from two city zip codes.

Citizens began complaining about the change within the same month, but officials didn't start addressing the issue until October 2015. Hedman previously told The Detroit News that the EPA knew of the corrosion problem as early as April, however the information was not made public.

The EPA issued a statement earlier this week admitting its response was too slow, while at the same time laying blame with local and state levels, reported Reuters. "While EPA worked within the framework of the law to repeatedly and urgently communicate the steps the state needed to take to properly treat its water, those necessary (EPA) actions were not taken as quickly as they should have been," the EPA said.

The agency added that its oversight was impeded by "failures and resistance at the state and local levels to work with us in a forthright, transparent and proactive manner."

Upon determining that the city and state responses to the crisis "have been inadequate to protect public health and that these failures continue," McCarthy issued a new emergency policy on Thursday.

"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, according to Fox News.

Among other measures, the EPA will start testing Flint's tap water and posting the results online, according to The Huffington Post.