Darren Mack has reportedly been sighted in Mexico, police said Thursday, the most significant break in an international manhunt for the ex-pawn shop owner who is wanted for killing his wife and shooting the Reno judge handling their pending divorce 10 days ago.

At a hastily called news conference, investigators outlined the reported sightings at several locations, including Cabo San Lucas, La Paz, Mazatlan and around Puerto Vallarta.

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Mack contacted Washoe County District Attorney Dick Gammick earlier this week "and expressed a desire to surrender," Reno Police Chief Michael Poehlman said.

Investigators last communicated with him Wednesday when he was believed to be on the west coast of Mexico, based on comments he made and information the FBI developed, Poehlman said.

They attempted to negotiate his surrender, but he failed to turn himself in to the U.S. Consulate in Puerto Vallarta as he had agreed to do, he said.

Gammick said he talked directly with Mack.

"He would not tell me where he was at. I picked up on that based on conversations we had on where we would meet. We've never been able to accurately pinpoint him," Gammick said.