The five men and five women were in custody in the capital, Port-au-Prince after their arrests on Friday night. There are fears that traffickers could try to exploit the chaos and turmoil following Haiti's January 12 earthquake quake to engage in illegal adoptions.
One of the suspects, who says she is leader of an Idaho-based charity called New Life Children's Refuge, denied they had done anything wrong.
The suspects were detained at Malpasse, Haiti's main border crossing with the Dominican Republic, after Haitian police conducted a routine search of their vehicle.
Authorities said the Americans had no documents to prove they had cleared the adoption of the 33 children -- aged 2 months to 12 years -- through any embassy and no papers showing they were made orphans by the quake in the impoverished Caribbean country.
"This is totally illegal," said Yves Cristalin, Haiti's social affairs minister. "No children can leave Haiti without proper authorization and these people did not have that authorization."
U.S. authorities could not be reached for immediate comment on the arrests.
But Laura Sillsby from the Idaho group told Reuters from a jail cell at Haiti's Judicial Police headquarters, "We had permission from the Dominican Republic government to bring the children to an orphanage that we have there."
"We have a Baptist minister here (in Port-au-Prince) whose orphanage totally collapsed and he asked us to take the children to the orphanage in the Dominican Republic," Sillsby added.
"I was going to come back here to do the paperwork," Sillsby said. "They accuse us of children trafficking. This is something I would never do. We were not trying to do something wrong."
In addition to outright trafficking in children, authorities have voiced fears since the quake that legitimate aid groups may have flown earthquake orphans out of the country for adoption before efforts to find their parents had been exhausted.
As a result, the Haitian government halted many types of adoptions earlier this month.
There are no reliable estimates of the number of parentless and lost children at risk in Haiti's quake-shattered capital.
(Editing by Peter Cooney)