Trailer and clips of "The Invisible War," the Oscar-nominated documentary by Kirby Dick.

The companies that manufactured trailers for displaced New Orleans residents after Hurricane Katrina knew that the trailers contained unsafe levels of toxic formaldehyde, but failed to inform the public, congressional Democrats charged Wednesday.

By PBS News Hour

Almost 18 months after Hurricane Katrina devastated the Gulf Coast, thousands of its victims are still without health care. In the first of a two-part report, NewsHour health correspondent Susan Dentzer looks at how doctors are providing some temporary relief.