An eight-month investigation into poor treatment of animals at Australia Zoo's animal hospital has found no evidence its hospital staff deliberately mistreated animals.

The Queensland Government's Biosecurity Queensland investigated 31 allegations since 2015 against the hospital staff.

Eight-month investigation finds no case of animal cruelty at Australia Zoo. Credit:Ben Beaden

"Investigators did not identify any animal welfare offences and the standard of care being provided at the hospital was deemed to be excellent," the Biosecurity Queensland report found.

The hospital treated 5635 wild animals in 2015. It sees up to 70 koalas a month.