A 3-year-old boy was critically injured Thursday at a zoo in England after he appeared to have been forced inside a crocodile enclosure by an apparent stranger who was later arrested on suspicion of attempted murder, authorities said.

The Cambridgeshire Police said the stranger was a 30-year-old man from Norfolk, a county about 100 miles northeast of London. The attack happened around 1:30 p.m. local time at Johnsons of Old Hurst in Huntingdon, a family-run zoo outside Cambridge, authorities said.

It was not immediately clear whether the boy was thrown into the enclosure or how many crocodiles were involved.

The boy was taken to Addenbrooke’s Hospital in Cambridge with serious injuries, said the police, who in a social media post three hours after the attack described his condition as critical but stable.

“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,” Verity McCann, a detective inspector with the Cambridgeshire Police, said in a statement.

The hospital referred questions about the boy’s injuries to the Cambridgeshire Police, which said it could not release further details while it was investigating the episode.

In a statement posted on social media, the zoo said Thursday that it was praying for the boy and his family.

“Out of respect to the family, our Tropical House will remain closed until further notice,” said the zoo, which also referred inquiries to the police.

On its website, the zoo describes itself as home to more than 100 animals, including crocodiles, African lions and Bengal tigers.

For 80 British pounds (about $106) per person, visitors 16 years and older can book a 30-minute session to “meet and feed our snappy crocodiles,” according to the zoo, which allows 14- and 15-year-olds to accompany a paying adult.

Ben Obese-Jecty, a member of Parliament who represents the area, addressed the attack in a statement on social media Thursday.

“I would ask people to refrain from speculation online,” he wrote. “The police will provide an update with further information in due course.”

This article originally appeared in The New York Times.