BILLINGS, Mont. (AP) — Federal regulators' long-delayed clean-up for a Montana mining community where thousands have been sickened by asbestos contamination would leave some of the deadly material in the walls of houses, underground and elsewhere — stirring worries among residents about the possibility of future exposures.

The U.S. Environmental Protection Agency plan released Tuesday for Libby and the neighboring town of Troy calls for asbestos-containing vermiculite to be left behind where it presents minimal risk and can be safely managed.

The plan comes more than 15 years after media reports revealed widespread illness caused by asbestos dust from a W.R. Grace and Co. vermiculite mine.

Some Libby residents say the material left behind when the EPA is gone eventually could escape, during excavation work or home renovations.

"We've left a lot of this behind in these houses, and you always have the potential of people opening up that wall and running into it," said Mike Noble, who worked for 21 years for Grace as an electrician and suffers from a lung disease caused by asbestos. "The EPA is unwilling to address that because the EPA is saying it's safe as long as nobody touches it."

For the proposal to work, there must be enough money available in future years for local officials to provide the proper assistance to homeowners, contractors and others who might encounter vermiculite, said Noble, chairman of an EPA advisory group in Libby.

Health workers have estimated as many as 400 people have been killed and almost 3,000 sickened in the area.

Vermiculite from the Grace mine was used as insulation in millions of houses across the U.S. Contaminated waste from the mine was unwittingly used by many residents as a garden-soil additive and as fill for the local construction industry.

An EPA research panel concluded last year that even the slightest exposure to asbestos from Libby can scar lungs and cause other health problems.

The agency so far has spent $540 million removing a million cubic yards of dirt from more than 2,000 properties, and officials say Libby's air is now much safer.

About 300 to 500 properties could need further cleanup work. In many of those cases, EPA officials said property owners have refused access to the agency.

Airborne asbestos concentrations in the northwest Montana community of 3,000 are now comparable to levels in other cities, according to officials.

If Tuesday's proposal moves forward, following a two-month public comment period, officials said the EPA could wrap most of its work in Libby by the end of the decade.

"We've done most of the cleanup already," said EPA Libby team leader Rebecca Thomas. "We can finish the cleanup in the next three to five years, and then the community can move on and start thinking more about economic development."

The agency's proposal includes a number of "institutional controls" to manage the remaining asbestos. Those include zoning restrictions that would prohibit what activities are allowed on contaminated property, permit requirements for the disturbance of contaminated soil or building materials, and advisories issued to firefighters and others who might inadvertently encounter asbestos on the job.

Just how much asbestos is being left behind is uncertain: Agency officials have never fully documented how many homes and businesses were left with vermiculite in their walls after cleanup work was completed.

The Libby area remains for now in the EPA's Superfund program.

Eventually, the community likely will lose that status — and much of the federal funding that goes with it. At that point, oversight for the institutional controls will become the responsibility of local agencies and the Montana Department of Environmental Quality.

"We know they are going to work only if we can get the community to buy in," said Jeni Garcin-Flatow with the Montana Department of Environmental Quality.