Officials at the Erie Zoo say it could be several more weeks before we know for sure what killed Alcor. The 750 pound polar bear went into cardiac arrest just minutes after beginning his trip back to Erie, and could not be revived. A necropsy was performed on Alcor Tuesday at the New Bolton Center in Philadelphia - the same place where the bear underwent six hours of surgery to repair a broken leg. Preliminary results of the necropsy are, so far, inconclusive. More test results expected in a few days. Zoo spokesman Scott Mitchell says it does not look like anesthesia was a factor in Alcor`s death. Mitchell says it`s still too early to determine whether the zoo will bring in a new polar bear. It`s believed Alcor broke his leg while rough housing with his brother Mizar, who was visited by dozens of zoo-goers Tuesday.