Investigators have found two more witnesses to the killing of a police officer, but still have no clues to the whereabouts of the survivalist fugitives suspected of shooting him.

Cortez Police Chief Roy Lane said the two witnesses were traced through leads gathered during a police checkpoint Friday morning on County Road 27, where Officer Dale Claxton was shot to death May 29 after pulling up behind a stolen water truck.The witnesses had no new information, Lane said Wednesday. Police interviewed two other eyewitnesses shortly after the murder.

All the witnesses told police that a man in camouflage jumped out of the passenger side of the water truck and sprayed Claxton's patrol car with bullets. Police said the gun, a modified fully automatic SKS, belonged to Jason McVean, one of the suspects.

"All of our information seems to indicate that McVean was the leader of the group," Lane said.

Still at large are McVean, 26, of Durango and Alan "Monte" Pilon, 30, of Dove Creek. The third suspect, Robert Matthew Mason, 26, of Durango, was found dead from a self-inflicted gunshot wound to the head on June 4 near Bluff, Utah, as authorities closed in on him.

Authorities are waiting for the two surviving suspects to venture into the open, Lane said.

"We're hoping to see 105-degree weather, hot nights and some huge mosquitoes," he said.

"What is strange in this whole thing is that we have not had one (confirmed) sighting, one house broken into, a stolen car or an armed robbery," Lane said of McVean and Pilon's disappearance. "They might have some place where they're holed up, or they're dead. . . . Or maybe they're in Mexico."

Authorities have looked at the possibility that the men were involved in some paramilitary organization or larger criminal conspiracy but have found nothing that strongly links them to other suspects, Lane said.