The US Environmental Protection Agency ordered the state of Michigan today to take “immediate action to address serious and ongoing concerns” with the city of Flint’s drinking water system, which has been contaminated for more than 18 months with elevated levels of lead.

“EPA has determined that the City of Flint’s and the State of Michigan’s responses to the drinking water crisis in Flint have been inadequate to protect the public health and that these failures continue,” the order reads. The EPA will begin sampling Flint's tap water and publishing analysis results on its website and lead an independent investigation into what could have been done to prevent the crisis.

The water contamination crisis is embroiling both Michigan Governor Rick Snyder, who apologized to Flint residents this week before releasing hundreds of pages of email records, and the EPA, which said on Wednesday its response to the crisis had been too slow. Susan Hedman, the regional EPA chief for Michigan and the surrounding Midwest, also announced her resignation today, effective February 1st, over her failure to prevent the crisis and notify the public and EPA officials about the potential health risks.

EPA's Michigan and Midwest administrator has resigned

The crisis dates back to a decision in 2014 to switch Flint's water supply from the water system of nearby Detroit to the Flint River, a choice made while Flint was under the control of a state-appointed emergency manager seeking new money-saving measures. The city of Flint, with a population under 100,000, switched back to Detroit's Lake Huron system in October 2015 after a study by Flint's Hurley Medical Center determined the amount of children with elevated levels of lead in their blood had doubled after the water supply switch. The corrosive water of the Flint River is thought to have leeched lead from the city's water pipes.

Despite the switch, Flint residents had been consuming the contaminated water for months while petitions and protests failed to force city officials to change the water source. Exposure to unsafe amounts of lead can lead to anemia, kidney failure, brain damage, and other ailments in young children and infants, according to the World Health Organization. A group of parents have since filed a class-action lawsuit against Flint, the state, and several public officials. Snyder's email records indicate officials at nearly every level in Michigan failed to acknowledge the severity of the ongoing crisis and constantly squabbled over who was to blame and whether the issue was being politicized, according to The Washington Post.

Obama declared a federal emergency over the crisis last Saturday

The situation in Flint has attracted the attention of the White House, and President Obama declared a federal emergency last Saturday to direct federal funding to help solve the crisis. “What is inexplicable and inexcusable is once people figured out there was a problem and that there was lead in the water. The notion that immediately families were not notified, things were not shut down—that shouldn’t happen anywhere,” Obama, who met with Flint mayor Karen Weaver this week, told CBS News.