Taronga Zoo is investigating the failure of fence fastenings after five lions escaped from their enclosure.

The zoo is waiting for a full engineering report but early indications suggest the lions were able to leave the exhibit when fastenings on the mesh wire fence failed.

“This opening has now been secured, however the lions will not be back out on their main exhibit while we await further engineering advice,” the facility said in a statement.

If any repairs or reinforcements are needed, the zoo will need to seek approval from the NSW Department of Primary Industries before returning the lions to their main exhibit.

“Our absolute priority is to ensure the safety of our people and guests and the welfare of our animals,” the facility said.

“While the Zoo’s intention is to fully complete all works necessary as quickly as possible, the exact timing of the works schedule is dependent on the expert advice we receive.

The zoo said the lions, currently in a back-of-house area, remained well and had not had any adverse reactions as a result of their escape.

It thanked the public and Taronga’s community for their support.

“We also acknowledge again the quick and professional response by our staff and the exemplary co-operation of guests,” the zoo said.

“The zoo and its experiences remain open.”

Four lion cubs and their father were found outside their exhibit, but away from public areas, on Wednesday morning.

Four returned to their enclosure after about 10 minutes but keepers had to tranquillise one cub before returning it to captivity.