A post mortem report has shown a one-year-old child found dead with his mother at their home in Tennessee starved to death.

The bodies of Tiffany Spears and her infant son, Nicholas Crowder, were discovered at their home in Portland, Tennessee in the US in February, but the results have only just been released.

The findings show the 32-year-old had been dead for several days when she was found and the Sumner County Sheriff's Office was alerted.

It also said 15-month-old Nicholas, who had been strapped into a car seat that was left on a bedroom floor, had died of starvation and dehydration.

Both deaths were ruled accidental.

Chief of detectives for Sumner County Sheriffs Office, major Tim Bailey told Sky News that Ms Spears died of a fentanyl and methamphetamine overdose.

"The child made this case unusual. We, along with several other agencies, have seen an increase in fentanyl overdoses. It is awful," he said.

A three-year-old girl was also found inside the property and was taken to hospital.

"She could fend for herself so to speak, she could feed herself and get water. She was treated and released from the hospital the same day", Major Bailey added.

The report said it appeared the toddler had "tried to take care of the decedent for several days" noting that food was found in and around Nicholas's car seat.