A dog that killed a nine-month-old baby in Rogiet, southeast Wales, on Sunday was an XL bully, police have said.
The animal had been registered before a ban on the breed came into effect, Gwent Police said.
Assistant Chief Constable Vicki Townsend said: "While the dog in this case was registered as an XL bully, it was done so proactively before the ban came into effect.
"In preparation for the new law, when requesting a certificate of exemption, owners were not required to formally identify the dog's breed.
"In cases where a suspected banned breed is involved only a dog legislation officer (DLO) or a court-approved independent assessor can make an official determination."
No arrests have been made at this time, she said, adding the investigation is ongoing and official identification of the dog was necessary.
Gwent Police were called to an address in Rogiet, in Monmouthshire, southeast Wales, at around 6pm on Sunday.
The force said officers went to the scene in Crossway at around 6pm with paramedics from the Welsh Ambulance Service.
A nine-month-old baby was pronounced dead at the scene.
Police said the dog has been seized and removed from the property.
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"We understand that there is a significant amount of interest and concern about this incident, and we have seen the community rally together in this difficult time," Assistant Chief Constable Townsend said.
"It is our responsibility as a police service to ensure that the death of a baby boy is fully investigated and so we again urge people to be responsible, and to consider the impact that speculation, rumour and commentary can have on the family and on the integrity of our investigation."
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