A schoolboy needed surgery for facial injuries after being savaged by a dog.
The incident is believed to have taken place in a front garden of a house on Lupton Place on the Ryelands Estate in Lancaster.
The child suffered puncture wounds to his face and was admitted to Royal Lancaster Infirmary at which point the police were contacted.
He has since been transferred to the Royal Preston hospital for surgery.
A joint investigation involving Lancaster Police and specialist Police dog handlers is underway and a 33-year-old man from Lancaster has been arrested on suspicion of having a dog dangerously out of control in a public place.
He has been released on police bail until June 27.
A dog, suspected of being involved in the attack has been seized.
Enquiries are on-going to ascertain the full circumstances of what has happened and if the dog is a banned breed.
Inspector Geoff Tagg said: “I would urge anyone who witnessed the incident or has further information that could assist us to contact Lancaster police on 101 quoting log reference LC-20130522-1645.”
The incident occurred on May 22.