LAS VEGAS — Middleweight fighter Julio Cesar Chavez Jr. could be stripped of his $3 million purse, depending on the explanation he offers to Nevada boxing regulators about a positive test for marijuana after his first professional loss last weekend in Las Vegas, officials said Wednesday. Top Rank Inc. spokesman Lee Samuels said promoter Bob Arum was aware the 26-year-old Chavez tested positive for the banned substance. The commission can ban a fighter for one year and penalize him for up to 100 percent of his purse for a failed test, Kizer said. — AP