An eight-month-old boy died after being found unconscious in bed beside his father at their home in Sau Mau Ping yesterday.
Police arrested the 27-year-old father on suspicion of negligence. He was granted bail and no charge was laid as officers needed more time to investigate.
A police investigator said it was possible the baby was crushed while he and his father slept in the same bed.
"No apparent wounds were found on the infant and our officers were told the baby had been in good health," the officer said.
"We have to wait for the results of an autopsy to ascertain the cause of his death."
The mother, 23, returned to the family's home in Sau Chi House, Sau Mau Ping Estate, at about 2.45am and roused the father, who was lying next to their unconscious son. The mother then called police.
The toddler was taken to United Christian Hospital in Kwun Tong, where he was declared dead at 3.49am.
Against Child Abuse director Jessica Ho Oi-chu would not comment directly on the case but said that the group in general did not recommend that parents slept with their babies, as they might fall asleep and roll over accidentally.
The Social Welfare Department handled 729 new reports of child abuse in the first nine months of last year. A little more than one in 10 cases involved neglect.