An American who sold his construction business and travelled to Haiti to help earthquake victims has been arrested over allegations that he kidnapped an infant.

Paul Waggoner, co-founder of a group that provides medical supplies and transport for aid missions, is expected to be spend the next few months in Haiti's overcrowded National Penitentiary.

Waggoner and members of his organisation, Materials Management Relief Corps, said the 15-month-old baby he is accused of taking died at a hospital with fever and gastrointestinal distress in February.

At a hearing on Wednesday, Waggoner's lawyer showed a death certificate to prove the baby died months ago. But the child's father, Frantz Philistin, insists the boy is alive and his lawyer said he doubted the document was authentic.

The judge decided to open a three-month investigation into the allegations. Haitian law allows defendants to be imprisoned without charge during investigations.

"They don't tell you anything. They just leave you in the dark," Waggoner said as he was taken back to jail.

Philistin brought his baby boy, Keevins, to the private Haitian Community hospital in Petionville, where Waggoner was working as a volunteer, on 23 February.

Paul Sebring, who founded Materials Management Relief Corps with Waggoner, said the baby was in bad shape, desperately needing oxygen and suffering from days of fever. While doctors were tending to Keevins a 4.7-magnitude aftershock hit and many of the hospital staff fled.

Sebring said that Waggoner was helping to move supplies and direct patients but was not involved in any treatment. "Paul never treated or touched the child," he said. "He had nothing to do with the case."

Waggoner's supporters say Philistin was told his son was dead but would not take the body home, saying he did not have money for a funeral.

Sebring said the father returned at least five times. Waggoner accompanied him, trying to keep him calm.

After two days, the American aid workers say, the body was incinerated. When the father returned again and found that the body was no longer there, he became enraged.

"They came to me and say, 'Your baby is dead.' I said, 'Don't lie to me.' I tried to close his eyes and they opened again. I closed them again and they opened," he told AP. "I want to find my baby. I know my baby is alive."

Philistin filed a lawsuit against the hospital in March. Waggoner left the country fearing retribution from the father but returned soon after. Philistin spotted Waggoner and Sebring with several friends at in a restaurant on Sunday and called police. The Americans were arrested, though all but Waggoner were released.