Prosecutors said Wednesday that the 200-pound chimp tested positive for the anti-anxiety drug.
In interviews earlier this year, the chimp’s owner, Sandra Herold gave differing reports on whether she treated the agitated chimp with Xanax, an anti-anxiety drug that had not been prescribed for him.
She has also said the animal suffered from Lyme disease. A test for rabies was negative and results from a necropsy won't be available for weeks.
Stamford State's Attorney David Cohen said Wednesday that while results show the presence of Xanax in the chimpanzee's system, it's unclear whether the drug played a role in the attack.
Travis, attacked Nash on Feb. 16, leaving her with no hands, nose, lips or eyelids.
Doctors at Ohio's Cleveland Clinic say she is blind and faces two years of surgical procedures.
Nash's family is suing the chimp's owner, Sandra Herold for $50 million.