The town is part of a 40-square-mile area that the federal Environmental Protection Agency put on its Superfund list in 1983, years after lead and zinc mining companies pulled out.
In the 1990s, a study found elevated blood lead levels in Tar Creek-area children, and teachers began noticing years ago that students were learning more slowly and couldn't focus.
In 2006, a U.S. Army Corps of Engineers study found more than 100 homes in Picher were in danger of collapsing into old mines.
Last year, just weeks after residents gathered to mark the town's final days with a parade, a powerful tornado tore through the area, killing six people.
The $60 million voluntary buyout is expected to conclude this year.
Copyright 2009 The Associated Press.