The independent watchdog of the Environmental Protection Agency will investigate how the environmental regulator oversees state authorities that monitor drinking water quality in the wake of the lead water crisis in Michigan.

The EPA Office of the Inspector General announced Tuesday it would begin doing research on how the EPA conducts oversight on state environmental agencies that monitor drinking water quality. The investigation comes months after the EPA official in charge of Michigan resigned over her role in failing to prevent a lead water crisis in Flint, Mich.

"Our objectives are to evaluate how the EPA ensures that Safe Drinking Water Act primacy states monitor and report drinking water sampling results from public water systems, and to determine whether the EPA can improve its oversight of state drinking water sampling programs," stated a letter sent by the inspector general's office.

While states have primary responsibility for watching over the drinking water quality in their municipalities, it's the role of the EPA to make sure those state agencies are following proper procedures.

In Michigan, agency officials ignored an EPA official who raised concerns about how Michigan Department of Environmental Quality officials were dealing with complaints about the drinking water in Flint. Those state regulators are now facing criminal charges for breaking the Safe Water Drinking Act and deceiving residents by falsifying tests.

In April 2014, the state-controlled government of Flint decided to switch water sources from Lake Huron to the Flint River. The Flint River's water was so acidic that it caused the old lead pipes leading to the city's homes to decay, putting lead into the drinking water of many residents.

The eastern Michigan town of 100,000 people only recently emerged from a state of emergency related to the drinking water crisis. Residents are still unable to drink the water coming out of their taps without a filter.

The EPA Inspector General's Office is already conducting an investigation into how the crisis happened.