A man has been arrested on suspicion of murder after a 10-month-old girl died at a house.
The child was found unresponsive at a home in Crompton Street, Farnworth, near Bolton, at about 17:30 GMT on Friday, Greater Manchester Police said.
She was taken to hospital, where she died shortly after.
Police said the 22-year-old man was being held in custody for questioning and tests to find out how the baby died were due to be carried out later.
Det Ch Insp Stuart Wilkinson said: "The investigation team is determined to understand how and why this little girl died.
"We will be continuing with inquiries throughout the days and weeks ahead and I would encourage anyone who has information to please contact police."