A city in the US state of Texas is appealing to the public to help solve a mystery that took place at a zoo last month.

A strange image was captured at the Amarillo Zoo early May 21 outside of the fence of the facility.

"Was it a person with a strange hat who likes to walk at night? A large coyote on its hind legs? A Chupacabra? It is a mystery – for Amarillo to help solve," authorities said on their website.

They said the strange visitor is for now an Unidentified Amarillo Object, or UAO.

"Perhaps Amarillo has a better explanation. In the spirit of fun if not curiosity, the City of Amarillo is letting the public offer ideas on the identity of the UAO," they said.

"It is important to note that this entity was outside the Amarillo Zoo. There were no signs of attempted entry into the zoo. No animals or individuals were harmed. There were no signs of criminal activity or vandalism," said City of Amarillo Director of Parks and Recreation Michael Kashuba.

“It is definitely a strange and interesting image. Maybe Amarillo can help solve the mystery of our UAO," he added./agencies