SWEENEY CANYON, Wyo. - The construction began last summer, stirring up dust that wafted down this desert valley and into a small community of off-the-grid homes.

As many as 20 heavy trucks a day hauling construction materials and equipment rumbled down the valley's main gravel road, passing into a gate marked with a "No Trespassing" sign. Helicopters flew in sling loads of cargo. Powerful work lights lit up the valley at night.

Public planners in southwest Wyoming's Sweetwater County - a sagebrush expanse roughly the size of Massachusetts - say the contractor hired for the project has told them it intends to build a 22,000-square-foot underground storage vault to store documents.

Whose documents exactly? Apparently, the writings of the late L. Ron Hubbard, the Church of Scientology's founder, and other church records.

But plans remain vague. County land use planner John Barton said the county also has been told the vault might hold any number of things besides documents.

"We've had everything from underground housing of sheep or hay," Barton said. "We've had cemetery discussed. We've had mining discussed."

The contractor, International Ground Support Systems of Santa Fe, N.M., also has said it plans to build a 3,500-square-foot caretaker house and an airstrip, county officials say. But they allege that IGSS has failed to apply for two required permits for work done so far.

The mysterious project has riled some neighbors, who value the solitude of their remote community, located about 150 miles east of Salt Lake City.

"I don't care if it's Church of Scientology, the Roman Catholic Church or, you know, Kraft Foods," Barton said. "We have development activity occurring - has occurred and, rumor has it, continues to occur - without required permits."

A local attorney representing IGSS, Robert Reese, said the earthwork already done is similar to improvements that would be made at any ranch. He said that's consistent with the site's agricultural zoning and past use as a cattle ranch. Therefore, he said, the contractor hasn't needed to get a permit.

"Our position is that everything that has been done so far falls well within the agricultural use and no permit is required," Reese said.

IGSS has a majority ownership stake in the 3,500-acre property along with a handful of locals who otherwise don't appear to be directly involved in the project, according to county officials.

Neither the Los Angeles-based Church of Scientology - a roughly 50-year-old religion noted for its unconventional beliefs and celebrity followers - nor IGSS officials returned several phone messages seeking more information about the project.

However, an entity called the Church of Spiritual Technology has been known to build underground vaults to store Scientology documents, including near Petrolia, Calif., and Trementina, N.M. According to records from Humbolt County, Calif., IGSS received a permit in 1990 to build the Petrolia vault for the Church of Spiritual Technology, which is based in Los Angeles.

The Church of Spiritual Technology doesn't have a listed phone number.

The Church of Spiritual Technology and the Church of Scientology are linked, according to Larry Brennan, of Bow, N.H., a former Scientologist who now writes a blog about the religion.

The Church of Spiritual Technology holds Scientology's copyrights and trademarks and stores church documents in underground vaults to preserve the religion in case of nuclear war, he said.

The developer's lack of permits prompted the county to issue a stop-work order in September. When work didn't stop, the planners referred the matter to County Attorney Brett Johnson, who said he's contemplating legal action if work continues without a permit.

"There's been a lot of earth moved. It's quite clear that they're preparing to do a lot more work and we just want them to come in and get the proper permits," Johnson said.

John Ledford lives in a solar-powered home within sight of the construction zone. He said the project has stirred up considerable dust and he worries that the construction could cause his water well to run dry.

"They've ruined the road, and we live with the fact that the road has gotten ruined. But the air and the water? It's just not right," Ledford said.

IGSS attorney Reese said that far from doing harm, the company has improved the property.

"They're doing nothing but agricultural work out there in the last couple of months," Reese said. "They've got grazing permits, cattle are being raised, they were cleaning stream beds, fixing up the property, getting a lot of trash out there. It's much nicer than it was."