The U.S. Environmental Protection Agency pointed the finger at Michigan officials on Tuesday for "resistance" to working with federal regulators to make the drinking water in Flint safe.
"What happened in Flint should not have happened," the agency said in a statement to NBC News. "We must ensure this situation never happens again."
Emails made public through record requests show that EPA officials knew as early as February 2015 that Flint residents might be drinking lead-tainted water because of high levels found at a home.
The emails, obtained by researchers at Virginia Tech, revealed that in April 2015, the EPA learned that the water from the Flint River was not being treated for corrosion control, which upped the risk of contamination.
An EPA water expert, Miguel Del Toral, wrote an internal memo in June 2015 that said the situation was a "major concern" and that Flint's testing methods could underestimate the amount of lead in the water.
The memo was leaked by the ACLU, prompting an EPA administrator to apologize to state environmental officials, and spurring the state Department of Environmental Quality to bash Del Toral as a "rogue employee."
Behind the scenes, the EPA and the state were clashing on whether Michigan needed to treat the water in order to control corrosion, a July 2015 email shows.
In its statement on Tuesday, hours before Michigan Gov. Rick Snyder was to address the crisis in a major speech, the EPA placed blame squarely on state and local authorities.
"Under the Safe Drinking Water Act, the state of Michigan was responsible for implementing the regulations to protect their residents' drinking water. 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 actions were not taken as quickly as they should have been," the agency said.
"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 situation in Flint — of a large system switching from purchasing treated water to untreated water — is highly unusual. EPA's ability to oversee [state] management of that situation was impacted by failures and resistance at the state and local levels to work with us in a forthright, transparent and proactive manner consistent with the seriousness of the risks to public health."
The EPA wasn't quite as critical in November, when a top water official said in a memo to underlings that "different possible interpretations" of a rule governing corrosion control might have played a role in the state's failure to take immediate action.
The water crisis in Flint began when the city stopped buying its supply from Detroit to save money and started getting it from the Flint River.
Despite repeated assurances the water was safe to drink by government officials, thousands of children were exposed to toxic lead, cases of Legionnaires' disease spiked, and other contaminants, including bacteria, forced residents to boil water.
Federal and state prosecutors have launched investigations.