LANSING, Mich. — Michigan’s Republican attorney general has named a former prosecutor to spearhead an investigation into the process that left Flint’s drinking water tainted with lead, though Democrats questioned whether the special counsel would be impartial.

Attorney General Bill Schuette said Monday that Todd Flood, a former assistant prosecutor for Wayne County, which includes Detroit, will lead the probe and be joined by Andy Arena, a retired head of Detroit’s FBI office.

Schuette said the two would play key roles in the investigation and prevent conflicts of interest since the attorney general’s office also defends the state. Both will report to Schuette, who promised they would provide an “experienced and independent review of all the facts and circumstances.”

He dismissed any concerns about Flood, who is now in private practice and has donated to candidates from both parties, including the maximum allowable amount to Schuette.

“I don’t care who he (Flood) has given money to, Republican (or) Democrat. It doesn’t matter,” Schuette said. “This is about conducting a thorough, exhaustive, complete investigation. That’s what we’re doing.”

It is unclear at this point if the probe could result in criminal or civil charges. The investigation could focus on whether environmental laws were broken or if there was official misconduct in the process that left Flint’s drinking water contaminated.

Flood declined to discuss which laws may have been broken, except to note “a plethora of laws” could be used and there are prohibitions against misconduct by public officials.

Schuette gave no timetable for the investigation.

Flint switched from Detroit’s municipal water system while under emergency state financial management and began drawing from the Flint River in 2014 to save money, but the water was not properly treated. Residents have been urged to use bottled water and to put filters on faucets.

Republican Gov. Rick Snyder has been a focus of criticism, but Schuette said political affiliations would not be a factor there either.

Democrats noted state records show Flood gave $3,000 to Snyder’s campaigns and the maximum $10,200 to Schuette over the 2010 and 2014 election cycles. Flood also gave $1,200 to former Democratic Gov. Jennifer Granholm and donated to various judicial candidates.