National Zoo suffers another loss.

The deaths of two Red Pandas is being investigated at the National Zoo, with rat poison coming under suspicion. Three zoo-keepers who entered the exhibit also fell ill after removing the pair, aged 5 1/2 and 7 1/2, from their exhibit." Officials said they were investigating whether a new rat control method being used at the zoo -- using poisonous pellets buried deep in the ground -- could have contributed to the animals' deaths. Hoage said the rat bait is used under "tightly controlled" conditions, but the possibility of poisoning exists and authorities were looking into it.

The developments followed several recent deaths among the zoo's older animals, including a lion, a white tiger, two adult giraffes and a seal. On Friday, zoo officials said the lion died from complications from anesthesia administered during a medical exam. The tiger was euthanized because of age-related osteoarthritis. The giraffes suffered from digestive problems, and the seal died of heart disease."