The High Park Zoo closed early Saturday after a bison at the zoo unexpectedly died.

One of four bison at the zoo died today, Toronto Parks spokesperson Mathew Cutler said in an email.

Cutler said the zoo was surprised by the large animal’s death, as it had no recent history of illness.  

“We have closed the zoo until tomorrow to remove the animal and return the zoo to normal operations,” Cutler said.

He said the zoo will be investigating the cause of death.