The XL bully, which is believed to have escaped from a nearby property shortly before the attack, remained in police kennels, a force spokesperson said.
A government ban on the breed comes into force in England and Wales in February, with owners having to apply for an exemption in advance if they want to keep their pets.
Ch Insp Emma Cheney said dog owners were responsible for their animal’s actions wherever they were.
“If your dog causes fear or harm, it will be you, the owner, who is held accountable and, in some cases, put before the courts.”