Boy was gasping for breath: step dad

A man questioned over the suspicious death of a toddler north of Brisbane has told of finding the boy blue and gasping for breath in his bed.

Police questioned the boy's 35-year-old stepfather after the child's body was found at a Caboolture home about 12.30am on Saturday.

Police have said the 21-month-old suffered injuries, but have not provided details.

The boy's stepfather has been questioned and released without charge and he's told the media he loved the boy like his own.

"He was my son and I loved him," the man told the Nine Network.

"I put him to bed and I just gave him a bottle. It was just like a normal night. I took the bottle out and picked him up and he was blue and trying to gasp for air."

Police are awaiting the results of a post-mortem examination.