OMAHA (Reuters) - Two chimpanzees at a Nebraska zoo attacked a keeper and bit off two of her fingers, police said on Saturday.

The keeper at the Riverside Discovery Center in Scottsbluff, Nebraska, was petting a 40-year-old chimpanzee on Friday who apparently did not want to be touched, according to police.

When the chimp grabbed the keeper’s hand, the keeper started screaming, causing the chimp to scream, police said. This attracted another chimp, who also grabbed the keeper’s hand.

The chimps bit, and the keeper lost her index finger and a ring finger on one hand at the knuckles, police said. The middle finger had a laceration but was not bitten off.

Anne Janes, executive director of the zoo in western Nebraska town, said the woman’s fingers were recovered, and she was taken to a Scottsbluff hospital for treatment.