FLINT, MI -- Additional criminal charges are expected to be announced by Attorney General Bill Schuette in a news conference Tuesday, Dec. 20.

Schuette's office issued a statement Monday, Dec. 19, not naming names, but saying the attorney general, special Flint water prosecutor Todd Flood and Genesee County Prosecutor David Leyton will announce the new charges in Flint Tuesday morning.

Two similar press conferences called by Schuette in 2016 have been followed by the arraignment of a total of nine defendants -- one city of Flint and eight state of Michigan government employees who have been charged with criminal wrongdoing tied to the condition of Flint's water.

The announcement includes no information about how many individuals are expected to be charged Tuesday or the nature of those charges, and Andrea Bitely, a spokeswoman for the attorney general, would not comment further.

Schuette announced an investigation aimed at determining criminal responsibility for what happened to the city's water system nearly a year ago.

The investigation came after the level of lead in Flint's water spiked after the city, while being run by a state-appointed emergency manager, changed its water source to the Flint River in April 2014.

Regulators at the Michigan Department of Environmental Quality did not require the city to treat the river water to make it less corrosive, and Schuette has claimed DEQ and Michigan Department of Health and Human Services workers committed crimes including misconduct in office, willful neglect of duty, tampering with evidence and conspiracy.

Prosecutors claim some employees from DHHS discovered Flint children were being poisoned by lead but suppressed the information and have also studied the department's role in remaining silent about a suspected link between Flint water and a Legionnaires' disease outbreak.