An estimated $500,000 worth of jewels was reported stolen from three gem dealers when they were stopped by a flat tire that may have been punctured by the thieves, Santa Monica police said. The independent dealers from Texas were driving away from a hotel in the 1800 block of Ocean Avenue on their way to Los Angeles International Airport after a gem show when someone blocked their rental car briefly, Police Sgt. Steve Brackett said. A few blocks away, the tire went flat, and two of the dealers left to get help. While the third dealer was engaged in conversation with a stranger, someone else apparently opened a car door and took the jewels.