(CNN) -- The U.S. is keeping close watch on the case of an American relief worker jailed in Haiti under suspicion of kidnapping a 15-month-old boy, the State Department said Friday, but it remains unclear whether the U.S. is working for Paul Waggoner's release.

"We have monitored his court appearances and continue to track the case closely," said P.J. Crowley, spokesman for the State Department.

A Haitian judge concluded after a hearing Wednesday that sufficient evidence exists to hold Waggoner while investigators evaluate a man's complaint that the American kidnapped his critically ill son from a hospital, according to Jon Piechowski, a spokesman for the U.S. Embassy in Haiti.

Waggoner is the co-founder of Materials Management Relief Corps, a humanitarian organization that seeks to provide logistical support to medical workers in Haiti, where a major earthquake caused extensive damage in January.

Waggoner was working at the Haitian Community Hospital in Petionville in February when a Haitian man sought treatment for his 15-month-old son.

Accounts differ as to what happened next, but the father believes the child survived and that Waggoner kidnapped him, Piechowski said.

Waggoner's supporters, including two physicians, have said the child died, and his body was cremated because the father would not claim the remains.

Dr. Kenneth Adams, a volunteer physician on staff at the Haitian Community Hospital, said he was present when the child's father returned to see his son and "witnessed as the father looked at the baby for several minutes, waiting for the baby to breathe."

The man took pictures with the deceased baby before he left, Adams said.

The father filed a complaint against Waggoner in March. Piechowski said Waggoner left Haiti without answering the accusations and was arrested December 12 after returning to the country.

Repeated efforts to contact Haitian government officials were unsuccessful Friday.

One account provided by supporters say the father handed Waggoner the child at the hospital. Another says Waggoner may have transported the child to the hospital.

Regardless, Waggoner had nothing to do with the child's care, according to his supporters.

"I was there through the whole thing, and what kills me is that Paul basically had nothing to do with the whole situation," said Jeff Quinlan, who said he was working as director of security at the hospital when the child arrived.

Quinlan said he told the father that the boy had died and instructed him to return within 24 hours to take the body. But he said the father instead returned with a "witch doctor" claiming the child was still alive.

Quinlan and Waggoner's organization said a doctor who treated the boy has signed an affidavit confirming that the child died, saying that the father had viewed the body and that he had declined to claim the remains because he did not have resources to bury the child.

Quinlan said he believes Haitian authorities are trying to extort money from Waggoner, who is being held in the National Penitentiary in Port-au-Prince.

Waggoner's sister said she is concerned for his well-being.

"The cells are made for about 10 people, and an average of 70 per cell is the current population," Randi Waggoner Lightner said. "There is nowhere for them to sleep; they don't get baths; water is unsafe if existent."

The State Department has maintained contact with Waggoner's family, Crowley said, and has "kept his family fully informed."

In February, 10 U.S. missionaries were charged with kidnapping over accusations that they tried to take 33 children out of the country without their parents' approval.

Ultimately, all were released and have since returned to the United States.

CNN's Danielle Dellorto, Salma Abdelaziz and Umaro Djau contributed to this report.