Another company has transferred federal energy leases to a conservation group, further reducing the possibility of natural-gas development on public lands along Montana's wildlife-rich Rocky Mountain Front.

Trout Unlimited said Tuesday that it received leases the Kohlman Co. held for potential gas work on the Front, the rugged expanse where the mountains meet the plains for about 100 miles south of Glacier National Park. Trout Unlimited, which has joined other groups in declaring the Front too environmentally sensitive for oil or gas drilling, said it intends to return those leases to the federal government.

''The public lands of the Front are some of the wildest country in the lower 48 states,'' Gene Sentz of the Coalition to Protect the Rocky Mountain Front said Tuesday. ''We've been working more than 30 years now to try to keep them undeveloped.''

The lease transfer is atop earlier deals that moved Front leases into the hands of conservationists, who then transferred them to the federal government.

With the latest agreement, four companies have sold or donated leases on some 63,000 acres of the Front during the last two years. Conservationists would like an end to energy leases on about twice that much land, said the coalition's Chris Mehl.

Trout Unlimited said it received Kohlman leases on 33,411 acres in the Front's Badger-Two Medicine area, a place of spiritual significance to the Blackfeet Tribe. Officials with Trout Unlimited would not discuss terms of the deal. Mehl said Kohlman sold the leases to the trout advocacy group.

Efforts to reach Kohlman, which Mehl described as a Billings-based business, were unsuccessful on Tuesday.

There is no published phone number for the company, and the Montana Board of Oil and Gas said it had no contact information. Trout Unlimited's Chris Hunt said he did not have a phone number for Kohlman and even if he did, he could not release it, because the company did not wish to be contacted.

The Bush administration announced in 2004 that the Rocky Mountain Front in Montana would be off limits to new oil and gas development, at least until a complete study of the area took place. The administration said such a study had not been launched, it would take a couple of years to finish and it would not be done before the end of a second Bush term in January 2009.

The Interior Department said in 2004 that the elapsing time would allow owners of Front leases to explore selling them as conservation groups worked to head off energy development. Legislation advanced by Montana's U.S. senators in 2006 put the Front off limits to future leasing, and established mechanisms for the voluntary reduction of existing leases.

In 1997, the Lewis and Clark National Forest supervisor at the time placed a moratorium on petroleum development on the Rocky Mountain Front, an area the Bush administration's energy plan had identified as an important source of natural gas.

The supervisor was Gloria Flora, who said Tuesday that there has been no confirmation of petroleum resources in the Badger-Two Medicine. ''Somebody would have to have really deep pockets, and a really high sense of optimism, to even suggest that they would want to drill up there,'' said Flora, who has left the Forest Service and works on public-lands issues from Helena.