Haitian police have arrested 10 United States citizens caught trying to take 33 children out of the earthquake-stricken country in a suspected illicit adoption scheme, authorities say.

Authorities fear traffickers could try to exploit the chaos and turmoil following Haiti's January 12 earthquake quake to engage in illegal adoptions.

But one of the suspects, who says she is leader of an Idaho-based charity called New Life Children's Refuge (NCLR), denies they have done anything wrong.

The five men and five women are in custody in the capital Port-au-Prince after their arrests on Friday night.

They 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 - and no papers showing the children were made orphans by the quake.

Yves Cristalin, Haiti's social affairs minister, says the incident is "totally illegal".

"No children can leave Haiti without proper authorisation and these people did not have that authorisation," he said.

But Laura Sillsby from the Idaho group NCLR says the group has done nothing wrong.

"We had permission from the Dominican Republic Government to bring the children to an orphanage that we have there," she said.

"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. I was going to come back here to do the paperwork.

"They accuse us of children trafficking. This is something I would never do. We were not trying to do something wrong."

US authorities could not be reached for immediate comment on the arrests.

In addition to outright trafficking in children, authorities have voiced fears 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.

-Reuters