The FDA has an “open and ongoing investigation” of imported chicken jerky treats from various manufacturers, a spokesman for the agency wrote in an email. Despite testing, no toxin has been identified that would account for the incidents. That hasn’t stopped a lawsuit filed in April in Chicago by a pet owner who claims Waggin’ Train treats killed his 9-year-old Pomeranian named Cleopatra. The suit, which is seeking class-action status, names the manufacturer Nestle Purina PetCare and Wal-Mart Stores Inc., where he bought the treats. (The product is sold by many retailers.) “We believe the claims are without merit and we plan to vigorously defend ourselves,” said Keith Schopp, spokesman for Waggin’ Train, a pet snack company purchased by food giant Nestle Purina in 2010. The product was already being produced in China, Schopp said, when Waggin’ Train was purchased. Consumers in China prefer the dark meat of a chicken, making the supply of white meat used for jerky plentiful there, he said, adding that production facilities in China are closely monitored for quality and safety.