A one-year-old boy has died in hospital after being attacked by a pet dog at his home in Leeds.
The boy died a short time later at Leeds General Infirmary
The attack took place in Tinshill in the north of the city on Monday afternoon, West Yorkshire Police said.
The child was taken to Leeds General Infirmary, but died a short time later as a result of his injuries.
Leeds City Council officials removed two dogs from the house. The dog which attacked the boy was due to be destroyed on Tuesday afternoon.
"A family liaison officer has been appointed to work closely with the family to support them through this difficult time," a police spokeswoman said.
The West Yorkshire coroner has been informed of the boy's death.
Police inquiries are continuing into the incident. No arrests have been made.
Early reports suggested the dog involved was an American pit bull terrier, but it is now unclear which breed attacked the boy.
A Leeds City Council spokesman described the two dogs they were holding as "bullmastiff types".
One dog was due to be destroyed on Tuesday, while the other was being picked up by its owners, he said.
RSPCA spokeswoman Heather Holmes said: "This is very sad news, and our sympathy goes out to the child's family and friends.
"To avoid any similarly tragic accidents occurring, we would urge owners to ensure that their dog, of whatever breed, is always supervised when near children or other animals, especially during hot weather, which can make even the most docile of animals become suddenly aggressive.
"Any dog has the potential to attack if provoked. As well as hot weather, noise, unpredictable behaviour and other factors can cause a usually friendly animal to bite."
A Defra spokesman told BBC News that in such cases officials look at the characteristics of the dog involved to decide whether it falls under the type of breeds banned by the Dangerous Dogs Act.
"Often animals described as American bull dogs have characteristics of pit bull terriers. It is very much a decision of front line authorities to make that judgement," he said.
The 1991 act was brought in following a series of attacks on young children.
The last fatality involving a dog attack is thought to have been just before Christmas in 1994, when a bull terrier savaged a month-old girl in Preston, Lancashire.