A premature baby declared dead by doctors at a hospital in Paraguay was found to be alive hours later when he was taken home for a funeral wake.

José Alvarenga said he discovered his son was alive after he heard crying from the box in which he was placed.

The baby is now back at the same hospital's intensive care unit and is reported to be in a stable condition.

The head of paediatric care at the hospital said a doctor had not properly checked the infant's vital signs. "This is a very unusual case," he said, adding that an investigation into the incident would be carried out.

A doctor who works at the hospital's maternity unit said staff had tried to revive the baby for an hour before declaring him dead.

"His pulse was so low that it was undetect­able," Aida Notario said.

According to medical records, the baby weigh­ed only 500g. The smallest on record was an American baby who weighed just 280g, born at less than 22 weeks.