A 30-year-old man has been arrested on suspicion of attempted murder after a three-year-old boy suffered critical injuries after entering a crocodile enclosure at a zoo near Huntingdon, England.

Axar.az reports, citing the BBC, that Cambridgeshire Police said the suspect and the boy were not believed to know each other.

The boy was taken to Addenbrooke's Hospital with serious injuries and remains in a critical but stable condition.

Zoo owner Andy Johnson said his wife, Tracey, entered the enclosure in an attempt to help the child.

Detective Inspector Verity McCann said police were working to establish the circumstances surrounding the incident.

“At this stage, we are speaking to people who were at the zoo at the time of this distressing incident to understand more about the circumstances,” she said.

The suspect has since been released on bail after being deemed “unfit to interview,” police said.

The zoo’s Tropical House, where the crocodiles are kept, has been closed until further notice.