Michigan's attorney general filed more criminal charges Tuesday linked to the probe of lead-tainted water Flint, targeting two state-appointed emergency managers running the troubled city as the crisis erupted in 2014.
The two former managers face four new charges, including conspiracy and misconduct in office, for their roles in the crisis, in which inadequately treated water from a local river corroded residential pipes carrying water to an estimated 100,000 people.
A federal probe later showed that state officials knew about the contamination for more than a year, before local residents were informed of the crisis.
Thirteen people have so far been charged in the investigation, which spans an 18-month period that began in April 2014.
Earlier this month, scientists who first detected the contamination said lead levels were continuing to drop in large parts of the city as lead-lined pipes in the city were replaced.
However, Virginia Tech scientist Marc Edwards urged Flint residents to continue using water filters on kitchen faucets until all old lead pipes in the city have been replaced.