San Juan County Sheriff Mike Lacy threw in the towel on the manhunt for two fugitive cop killers here Friday, saying all the available resources are exhausted. He handed the investigation over to the Federal Bureau of Investigation.

"All of our leads have been followed through," Lacy said. "We have found nothing." Jason McVean, 26, of Durango, Colo., and Alan "Monte" Pilon, 30, of Dove Creek, Colo., continue to elude scores of searchers who have spent five weeks tracking them through southern Utah badlands.The cost of Lacy's "nothing" comes high.

Loosely tallied, the cost equals one police officer's life; wounds to three other officers; thousands of man-hours of combing through canyons, over high mountain deserts and through riverbank brush; and up to millions of dollars in expenditures for high-tech surveillance equipment, such as night vision glasses and military helicopters with heat sensors that should be able to find a needle in a haystack.

An empty-handed Lacy says it's time to move on.

"We're tired. We've done everything we can to apprehend these guys at this particular time," he said. "We'll still be following up on leads, but we're scaling back this particular operation. We're dropping back to a support role."

That may mean that nothing also came at the cost of Lacy's relationship with federal agencies such as the FBI, the Bureau of Land Management and the U.S. Forest Service.

All have been party to the search efforts, but cooperation among the agencies broke down this week over discussions debating the wisdom of setting fire to trees and brush along the San Juan River banks. The objective was to open up the dense landscape for better surveillance. But disagreements arose over the method of setting those fires and Lacy ultimately went ahead with only limited support.

Officers did light fires in the river bottoms Thursday, but when they were snuffed out by Friday morning only about one mile of a proposed six-mile burn area had actually been cleared. Early Friday, Lacy talked about setting at least one additional fire, but that never happened.

The plan was abandoned mostly because continued negotiations among the agencies remained flat, Lacy said. That's when he decided to call it quits, and hand the ball to the federal agencies, apparently without any advance notice.

"This is the first time they're hearing it," Lacy told a group of reporters gathered near the search command post in Montezuma Creek Friday afternoon.

Lacy's decision means an end to the daily patrolling of the river bluffs in the 14-mile area between Montezuma Creek and Bluff, 14 miles to the east. It also means an end to roadblocks and an end to searches of caves, rock outcroppings and abandoned mines that have gone on here at one level or another over the past month.

Officially, the manhunt began May 29 when McVean and Pilon, with another Colorado man, Robert Mason, 27, allegedly shot and killed Cortez, Colo., police officer Dale Claxton. Two other officers were wounded in an ensuing police chase.

On June 4, the search homed in on Bluff after Mason allegedly shot and wounded San Juan County sheriff's deputy Kelly Bradford. Mason was found a short time later, dead from a self-inflicted gunshot wound.

For weeks, the trail of the remaining fugitives, both highly trained in backcountry survival, has been cold. But it got hot again last weekend when a Montezuma Creek teenager saw two men trying to steal a water truck from a local oil company.

The girl positively identified Pilon and McVean from police photos.

At one point this week, police felt they may have been within inches of discovering the two men. New tracks along the river and positive "hits" from surveillance dogs, combined with the late night sounds of two men "giggling and playing" in the river had officers convinced the fugitives were within reach.

But by Saturday, searchers were again hot, tired and frustrated.

"We have a lot of resources out here, but we're just not able to catch them," said Lt. Tom Rett-berg, a helicopter pilot for the Utah Department of Public Safety. He helped monitor Thursday's fires from the air. "With the evidence they had, it seemed like we would catch them."

At some point police department budgets and officers can only give so much, he said.

"If there is frustration, it's that we want to put an end to this before anybody else gets hurt," he said.