Officials are yet to confirm the exact cause of the death but suspect that the deer died of poisoning.
Divisional Forest Officer Hemant Pandey said the cause of death would be known after autopsy but the sudden deaths shocked the forest department.
Sources said zoo staff spotted the dead deer when they went to feed them. The zoo which attracts scores of visitors every day is home to about 53 deer, 18 of them male.
Forest officials are not ruling out the possibility of poaching behind the deaths. Some of the deer were pregnant.