A US couple have been arrested after a one-year-old baby boy was found decomposing inside their bedroom closet.

The infant was found on Monday (30 October) in a tupperware box that was covered with blankets, police in Fayetteville, Arkansas said.

Tyler Hobbs, 21, was arrested for first-degree murder and abuse of the corpse, while the infant's mother, Maria Giron-Molina, was arrested for abuse of a corpse.

Detectives say the horrendous discovery came after Hobbs called 911 early Monday evening stating that the child had fallen down the stairs and started seizing.

He claimed the incident "happened a few days ago" and that he had panicked after he failed to revive the young boy, police said.

When officers arrived at the couple's home in North Leverett Avenue, they were pointed to a closet in the bedroom where Hobbs and Giron-Molina slept.

The decomposing baby was found inside a plastic container under some blankets. He was thought to have been there for around two weeks, with police saying they found bruising on his face.

Police said Hobbs later changed his story, telling officers that on 15 October the child had been "crying uncontrollably" and that he was suffering a headache.

"The child then knocked a picture frame and lamp off of a bedside table," a report by Fayetteville Police reads. "Angered at the child's refusal to calm down, [Hobbs] picked the child up and covered its mouth with his hand to 'muffle' the crying.

"Hobbs said the child hit and scratched him, so he shook the child back-and-forth. Hobbs said he blacked out, and when he 'came to', he saw the child was not breathing."

Hobbs, said to have been under the influence of cannabis at the time, claims he performed CPR in a bid to revive the child, but ultimately his attempts to save its life failed.

He allegedly told officers he panicked and put the boy in a plastic box and in the closet.

Giron-Molina told investigators that she saw blood on the sheets after Hobbs told her the boy had died after a fall at the park.

She said she was afraid of calling police after her son's death because she didn't want her other children taken away, according to the police report.

Police said the couple planned to give her other two children to relatives before contacting authorities.

Hobbs expressed remorse for his actions and said he did not intend to harm the child, police say.

The baby's body will be sent to the Arkansas State Crime Lab to determine cause of death.

Police say the investigation is ongoing.