The Bureau of Land Management is planning to lease nearly a half-million acres of its Utah holdings for oil and gas development in the largest lease sale the agency has ever held in the Beehive State.

Altogether, about 440,000 acres are to be auctioned in the May 16 lease offering. Two-thirds of the parcels were deferred during previous sales.

BLM spokeswoman Adrienne Babbitt said much of the drive behind this offering is interest in natural gas production. But some also reflects the ongoing oil interest in central Utah sparked by the discoveries of Wolverine Gas & Oil Corp.

Parcels that were deferred from earlier sales needed a "hard look" by the BLM to determine if they were appropriate for leasing, she said. Among the concerns was whether leasing would fit in with new land-use management plans, potential designation of Areas of Critical Environmental Concern, and Wild and Scenic River protection, she said.

In Nine Mile Canyon, a region with a huge amount of ancient structures and rock art, "we didn't end up offering any of the parcels down in the bottom of the canyon," she said.

Parcels that are to be offered in that region include land on top of a plateau, for example.

A state office leasing team has been helping with the analysis of the land. A reason for the large sale includes "just the consumer-driven market demand that we're seeing right now," Babbitt said.

Natural gas demand, she added, "is just going to rise."

Leasing is only a first step, and actual development may not take place for five to 10 years, she said.

Environmental groups could not be reached Tuesday for comment.

Lee J. Peacock, president of the Utah Petroleum Association, said the organization supports the leasing of most Utah acreage that is available under existing laws.

"We think it's clearly important that these be put into the mix and be allowed to go through the process," he said. "Just because a parcel is leased doesn't mean there will be significant oil and gas development. What it does mean is that there would be that option."

If development takes place, he said, the companies "would have to comply with all of the stringent environmental policies that are in place."

Kent Hoffman, the BLM's Utah director for lands and minerals, noted that the May sale is the most closely scrutinized yet and that the BLM made sure leasing certain parcels would not preclude options in new land-use plans the agency is preparing.

With an oil boom raging throughout much of Utah, demand for parcels continues to be high. Since 2002, according to the release, the average bid has grown from $10.25 an acre to $113.70.