West Mercia Police said the child died in hospital yesterday morning after paramedics were called to an address in Telford, Shropshire at around 8am.
A police spokesman said officers were awaiting the result of a post-mortem examination, and have launched an investigation to establish the precise circumstances of the death.
The spokesman said: 'Police and ambulance were called to an address in Woodside Road, Ketley, about a young baby that was unwell.
'He was taken to the Princess Royal Hospital in Telford by paramedics but died soon after.
'As in all cases of the death of a young child, West Mercia Police has launched an investigation to establish the exact circumstances.'
It is understood that the dog involved in the incident, thought to be a small family pet and not a dangerous dog, has been put down.
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