A woman has sustained severe injuries to an arm when she was attacked by a lion at an Australian zoo.

The Darling Downs Zoo in Queensland state said the 50-year-old woman was watching animal keepers working in the zoo’s carnivore precinct before opening hours on Sunday morning when she was attacked.

She was flown by helicopter from the rural town of Pilton to the state capital Brisbane where she underwent surgery. Her condition was stable, the zoo said in a statement, and several local media reported the woman lost the injured arm.

The zoo said staff were working with government workplace safety investigators to determine how the incident happened. The state government confirmed an investigation was underway.

The lion would not be put down as zoo reopened on Tuesday following the incident.