The state body that regulates power lines formally asked last week for a detailed study into burying parts of a proposed transmission line in Loudoun County, a move that heartened local officials and activists who have long insisted that such a technique be given serious consideration.

The State Corporation Commission ruled that a transmission line proposed by Dominion Virginia Power, which would run from south of Leesburg to the Hamilton area, is needed. That decision was cheered by a Dominion spokeswoman and matched last month's findings by an SCC hearing examiner who has overseen testimony in the case.

But on two major questions -- the path of the line and whether parts should be underground -- the commission indicated that it was not ready to accept the findings of the examiner, Howard P. Anderson Jr.

Anderson recommended an overhead line carried atop steel towers more than 100 feet tall, on a 12-mile path through southern Leesburg and along parts of the W&OD trail.

On Wednesday, the commission ordered Anderson to gather further evidence on the underground construction of some segments of the line. It also asked for more information, including costs and construction times, on Anderson's recommended route as well as on two alternative paths: a route south of Leesburg favored by Dominion and a route through Leesburg.

A commission official cautioned against reading too much into the order, saying there was no clear indication of what the SCC would decide after the next evidentiary hearing July 9 in Richmond.

"The main issue now basically involves the routes and undergrounding," said Katha Treanor, a commission spokeswoman. "The commission is trying to get more information. It just wants more details. . . . There's nothing in the commission's order that indicates that anything has been taken off the table, in terms of undergrounding or overheading lines. At this point, it's really anybody's guess what the commission will do."

But advocates of burying the line said the commission's call for a detailed look into the issue is significant given what they called Virginia's long history of giving short shrift to a technique widely used in other parts of the country and around the world.

"They have been against this consistently," said Patrick Sloyan Sr., a Paeonian Springs resident who has spearheaded efforts to put the line underground. "Suddenly it's gotten serious."

Sloyan attributed the commission's latest position, which he called "a back flip," to lobbying efforts and the bruising fight over a bigger Dominion project -- a proposed 240-mile Northern Virginia overhead transmission line that would cut through Frederick, Warren, Fauquier and Prince William counties before ending at a substation in southern Loudoun. He said those pressures have somewhat altered the political calculus in Richmond in fights over power lines.

Still, Sloyan argued that what he considers a misguided aversion to putting lines underground may ultimately prevail. "I still think it's an outside chance on putting it underground," he said.

Opponents of the proposed overhead lines say they would scar the landscape and lower property values.

Del. Joe T. May (R-Loudoun) said he was encouraged by the commission's latest move, especially its call for further inquiry into a newer, cheaper technology for burying lines.

"It appears that they are looking more closely at undergrounding," May said, adding that although he couldn't be certain the commission was not simply taking a perfunctory look, "it appears they are considering it as a legitimate alternative."

May, an inventor and engineer, accused Dominion of relying on inflated cost estimates for burying lines.

"Dominion Power got an engineering firm in Canada to prepare a proposal for under-grounding, and they deliberately made the costs very high," he said, pointing in particular to the estimates for cable and concrete.

On one proposed route, Dominion estimated overhead costs at more than $30 million and underground costs at $77 million, according to a commission document. May said such estimates do not include the costs to neighboring landowners if the lines hurt property values. He proposed legislation this year to require that such losses be considered by Dominion, but the bill was killed.

Le-Ha Anderson, Dominion's manager for media and community relations, disputed that the utility padded estimates for burying lines.

"We don't agree with that. We give an estimate based on the engineering, based on the cost of right of way. . . . It's comparable to the estimates that other utilities around the country would give," Anderson said. "What we've provided so far are estimates, and we believe they are accurate estimates."

The company opposes burying transmission lines, Anderson said, because of the expense and the difficulty finding underground failures. Sloyan contends that burying lines increases reliability.

"We take our commitment in making sure our customers have reliable electricity very seriously, so we work with legislators, we work with the community in every way possible to try to ensure we build for the future," Anderson said.