Federal regulators were aware that asbestos-contaminated bark and wood chips in Libby, Montana were being sold and used by local residents and government officials more than three years before they acknowledged it publicly, according to a letter from the Environmental Protection Agency, sent to U.S. Sen. Max Baucus.

Libby is the site of an EPA superfund, the result of the town receiving a “public health emergency” declaration in 2009 in response to the hazards of asbestos exposure and the higher than normal incidence rate of mesothelioma and other asbestos-related diseases.

After reading a report from The Associated Press discussing the use of the toxic materials, Baucus (D-Montana) requested further clarification from the EPA about the wood products.

In previous statements, the EPA said it knew as early as last fall that wood chips kept at a former lumber mill were being sold by a local economic development official. In a letter Baucus dated July 15, the EPA acknowledged knowing about the sales more than three years ago — as early as October 2007.

Baucus gained a commitment from the EPA that additional tests will be taken to confirm if the bark and wood chips are a health hazard.

“I’m watching to make sure the tests are performed thoroughly and transparently, and I’ll be here to hold EPA’s feet to the fire and make sure their response is up to par,” Baucus said in a statement. “We’ve got to get to the bottom of this quickly so Libby can continue to heal and begin to prosper.”

The EPA committed to perform activity-based sampling for Libby homeowners who have been exposed to the bark; to re-analyze wood chips to measure the quantity of asbestos fibers; and to conduct toxicology assessments for cancer and non-cancer health hazards.

Since the closing of W.R. Grace‘s asbestos-contaminated vermiculite mine in Libby in 1991, an estimated 400 people in the area have passed away from an asbestos-related disease.