A 22-year-old woman has suffered "devastating" facial and head injuries in an attack by a dog in Lincoln.The dog's owner has been arrested and the animal, believed to be an American pit bull, has been captured and put in kennels.
Armed police and a helicopter were deployed to search for the dog after the attack on Sunday.
A police spokesman said the skin on the woman's head had been "ripped back exposing her skull".
She also suffered "deep facial gouges on her cheeks," said Insp Michelle McIlroy, of Lincolnshire Police.
Residents in part of Lincoln were warned to stay in their homes during the night-time search for the animal.
The woman was taken to Lincoln County Hospital and was expected to have surgery later.
A 33-year-old man has been arrested on suspicion of having a dangerous dog out of control in a public place and will be questioned later.
Police searched an area near an old quarry off Outer Circle Road on the outskirts of the city on Sunday evening.
The area where the dog was thought to be was "contained" by police.
Insp McIlroy said it was thought magistrates would be likely to approve a destruction order for the dog.
"She has suffered quite devastating injuries. They are not described as life-threatening, but certainly life-changing," said Insp McIlroy.
"It is quite unusual for an adult to be attacked by a dog in this way - we hear about small children being attacked but it is unusual for an adult to be attacked."
Tests are being carried out on the dog to confirm the breed, police said.