Elijah Shemwell was found by his mother at his Belper home at Acorn Drive on January 2 and taken to hospital in Derby after she called an ambulance.
Police confirmed earlier this month that a 21-year-old woman and a 16-year-old boy were arrested in connection with Elijah’s death - however they were released pending further enquiries.
Area Coroner for Derbyshire Peter Nieto told the opening of Elijah’s inquest that the child had been in cardiac arrest for an estimated “55 minutes” when he arrived at hospital in Derby.
However doctors battled to keep the baby’s heart going and he was transferred to the Queen’s Medical Centre – where he was placed on life-support and a brain injury was diagnosed.
Mr Nieto said: “Due to his worsening condition he was assessed for brain stem death.
“On January 5 brain stem death was diagnosed by clinicians at the Queen’s Medical Centre.”
Elijah died the same day at the hospital where he was identified by his father.
In a postmortem examination conducted on January 7 Dr Stewart Hamilton gave his “current opinion” as to cause of death as a head injury.
However there were “other potential factors to be confirmed”.
Mr Nieto said: “I have reason to suspect that his death was not a natural causes death and there is the possibility that his death has arisen due to injury.”
He added: “This is a case where the police are still conducting an investigation and the latest information I have from the police is that two people were arrested in relation to Elijah’s death - a 21-year-old and a 16-year-old.
“They have been released on police bail until the end of this month.”
Mr Nieto said a pathologist was still awaiting confirmation of further postmortem investigations by a number of specialists - which were expected to take some time to be made available in reports.
He added: “The police investigation is still ongoing.”
The coroner set a review date for the inquest on May 23.
Detectives are currently reviewing CCTV footage of the area around Acorn Drive to piece together what happened on January 2.
They are appealing for anyone who may have private CCTV footage which may help to get in touch by phoning 101.