One of our great passions at FRONTLINE is investigating stories that others have moved on from or overlooked.

Tonight’s new documentary is a stellar example of that.

Flint’s Deadly Water is the result of two years of on-the-ground reporting from a team of FRONTLINE journalists — all of them Michigan natives — who set out to determine the true toll of the Flint water crisis. As it turns out, it is likely far worse than we knew.

Director Abby Ellis, reporters Kayla Ruble and Jacob Carah, and FRONTLINE Senior Editor Sarah Childress conducted exclusive interviews, pored over thousands of court records and internal state emails and documents, and undertook a sweeping analysis of every death in the county since the city’s water source was switched to the Flint River on April 25, 2014.

What they found reveals how a public health disaster that’s become known for the lead poisoning of thousands of children also spawned one of the largest outbreaks of Legionnaires’ disease in U.S. history.

In fact, as you’ll see in our documentary, we’ve found that there may have been about 70 more deaths from Legionnaires’ during the outbreak than the 12 that were officially recorded — and that an additional 20 patients who initially survived their diagnosis have since died of causes commonly linked to the disease.

It’s important to know that Legionnaires’ disease is a severe form of pneumonia that’s treatable if properly identified — yet, our team reports that government officials knew about the outbreak for over a year before alerting the public.

That’s just some of what you’ll learn in Flint’s Deadly Water. Featuring numerous sources who are speaking publicly for the first time, this comprehensive, richly detailed investigation expands our understanding of the Flint water crisis — and questions whether anyone will ever be held accountable. It’s a powerful example of the importance and urgency of locally based reporting in the public interest, and of sticking with a story after much of the national media has moved on.

After all, as you’ll see in this film, the water crisis is still far from over for the residents of Flint.

Flint’s Deadly Water premieres Tuesday, September 10 at 10/9c (check local listings). Tune in or stream on PBS, at pbs.org/frontline or on the PBS Video App.

– Raney Aronson-Rath
FRONTLINE Executive Producer