A man whose dog killed his niece could be prosecuted under the Dangerous Dogs Act after it was confirmed the animal was a type of pit bull terrier.
Ellie Lawrenson, five, died of severe head and neck injuries after being mauled at her grandmother's house in St Helens, Merseyside, on Monday.
On Tuesday, Ellie's family - including her uncle - laid flowers at the house.
Anyone convicted of owning a prohibited dog can face a £5,000 fine or six months in prison under the 1991 Act.
On Wednesday, further tributes to Ellie were paid by staff at the nursery she attended at Tower College in Rainhill.
A spokesperson said principal Rachel Oxley and the rest of the staff were deeply saddened by the "horrific attack".
"Ellie was a delightful, bright pupil who had a great deal to offer and will be missed by all of her friends, teachers and staff at the college," the spokesperson added.
Merseyside Police said post-mortem tests showed the dog was among the breeds prohibited by the Dangerous Dogs Act.
Pit bulls are one of four breeds banned under the legislation.
A Department for Environment, Food and Rural Affairs spokeswoman said: "If a person is found to be guilty of illegal possession of a prohibited dog they could face a £5,000 fine and/or six months in prison."
Two previous complaints had been made about the pet, which belonged to Ellie's uncle.
Supt Jon Ward, of Merseyside Police, said: "An assessment has been made by a recognised expert on the Dangerous Dogs Act, from the Metropolitan Police, and he has confirmed that the dog was a pit bull terrier type.
"The results of this post-mortem will now be included in the investigation and we will be speaking to all family members about the circumstances leading up to this tragedy.
"As soon as the investigation is completed, a report will be presented to the coroner and to the Crown Prosecution Service in terms of considering what offences, if any, have been committed."
Ellie was attacked in the early hours of Monday at the house in Knowles House Avenue in Eccleston.
She was staying with her grandmother, Jackie Simpson, while her mother and father went out to celebrate the New Year.
Ms Simpson, 45, suffered arm injuries before locking the dog outside. She has undergone surgery at Whiston Hospital.
Police have yet to speak to her about what happened.
The dog was shot dead by a police marksman following the attack.