AUGUSTA — In a divided vote, a legislative committee has endorsed a controversial proposal to rewrite Maine’s mining regulations after a months-long debate focused largely on a potential mine at an Aroostook County mountain laced with precious metals.

The 8-5 vote in the Environment and Natural Resources Committee on Thursday was an initial victory for those who have argued that Maine’s current laws are unnecessarily restrictive and have essentially shut down an industry that once employed thousands of workers across the state. Two Democrats, including Rep. John Martin of Eagle Lake in Aroostook County, joined Republicans in supporting the bill.

Opponents of the latest proposal, as well as a previous version that failed to pass the Legislature last year, warn that the rules could lead to polluted lakes and rivers while saddling taxpayers with the cleanup costs.

“I don’t think these (proposed) rules are substantially different from last year’s rules,” said Nick Bennett, senior scientist with the Natural Resources Council of Maine. “The Legislature rejected last year’s rules and they should be rejected again.”

The version of L.D. 750 endorsed by the committee lays out some site restrictions on mines – such as a prohibition on state parks and public reserved lands – as well as monitoring, closure and cleanup requirements on mining companies. The proposal would also require mining companies to provide “financial assurance” to cover potential environmental problems and require “perpetual treatment” of contamination for at least 20 years after a mine closes.

Lawmakers began reviewing Maine’s now 24-year-old mining rules in 2012 at the behest of timberland owner J.D. Irving Ltd. and Aroostook County lawmakers.

Irving, the state’s largest landowner, owns the land and mineral rights on Bald Mountain, a remote spot 35 miles west of Presque Isle that contains deposits of gold, silver and other minerals.

While Bald Mountain has dominated discussion of the mining rules, the Maine Geological Survey lists 10 sites of “significant known metallic mineral deposits” in the state.

The Maine Department of Environmental Protection proposed a set of rules last year, but the Democratic-controlled Legislature rejected the rules and Republican Gov. Paul Le-Page vetoed a bill directing the department to revise the rules. The most recent rules are intended to end the legislative standoff.

Jim Mitchell, an Augusta-based lobbyist representing Irving and its subsidiary, Aroostook Resources, said the Environment and Natural Resources Committee put in “an extraordinary amount of work to strengthen the rules.” Irving supports the latest compromise, which Mitchell described as “very, very tough” and providing adequate safeguards for water quality and the environment.

“Given the rules of the road are now clear, I think it is likely that companies will come forward to start looking at mining opportunities in Maine, starting at Bald Mountain,” Mitchell said.

Opponents plan to continue lobbying against the bill, however, as it heads to the House and Senate floor for consideration.

Bennett said the proposed rules would appear to allow mining on some public reserved lots, which are treated differently than public reserved lands in some areas of Maine law.

He also said the final wording on the “financial assurances” – wording that was proposed by Mitchell and Irving representatives on the day of the vote – is significantly weaker than the previous language.

Rep. Jeff McCabe, D-Skowhegan, also expressed concerns about the latest version.

“Clearly, many of us continue to have serious concerns about water quality and how it relates to public health and aquatic life, including iconic species like brook trout,” McCabe, the House Democratic leader, said in a statement.

“As they stand now, these rules do not go far enough to protect taxpayers from cleanup costs and our great ponds from pollution. These rules will have a high hurdle to clear in the House.”