Multiple media outlets reported Friday that a gorilla named Mike escaped his exhibit for about five minutes and injured a food service employee.
No details immediately were given on the worker's condition. The animal returned to his enclosure on his own.
Visitors were asked to go inside buildings or to leave the zoo for about 45 minutes Friday morning, but things were back to normal by noon.
A call to Riverbanks Zoo and Garden spokeswoman Lindsay Burke was not immediately returned.