Chadian authorities have detained the seven Spanish crew members of a plane chartered to fly more than 100 children to France.
The crew are being held along with nine French citizens - three journalists and six members of the French charity Zoe's Ark - in the eastern town of Abeche.
The charity says the children need medical treatment, but a BBC reporter says they appear to be in good health.
Inquiries also indicate they are not all orphans from Darfur, as Zoe's Ark
Staff from the United Nations children's agency, Unicef, said many of the children cry at night for their parents and say they are from villages in Chad.
A spokesperson for Zoe's Ark, Stephanie Lefebvre, has denied there was any plan to sell the children for adoption. She insisted the children had been sick and needed help.
But the French foreign ministry has condemned the charity's attempt to fly the children out of the country as "illegal and irresponsible". A court in Paris has launched a criminal investigation.
The BBC's Stephanie Hancock was among a group of reporters taken by Chadian authorities to the airport at Abeche, a town close to the Sudanese border, and shown the private charter plane still sitting on the runway where it was abandoned two days ago.
The reporters were later taken to the local police headquarters to see the 16 Westerners who were detained.
They are not held in prison cells but in a large room and are showing no signs of mistreatment, our correspondent says.
The seven Spaniards among the group are the plane's two pilots and five air stewards.
Zoe's Ark has denied there was any plan to sell the children for adoption
Spanish media have reported they are employees of the Barcelona-based charter company, Girjet. The company said it had provided transport for the charity but was not otherwise involved in the plan, media reported.
Chadian authorities initially have 72 hours to question the group, a period which expires on Sunday morning, but are expected to seek a further 48 hours to continue their inquiries.
It is still unclear whether charges will be brought against the Europeans, but the Chadian government has repeatedly said that what was attempted was illegal, our correspondent says.
The reporters were also taken to the orphanage in Abeche where the 103 children are being cared for by aid workers and UN staff.
Aid workers confirmed they were not treating any of the children for any serious illnesses or injuries.
The vast majority of the children are believed to be between three and five years old, with the oldest about eight or nine, and several babies no more than one-and-a-half, our correspondent says.
The president of the French national committee for Unicef said 48 of the children questioned so far appeared to be Chadian, not Sudanese.
"Our impression is that the majority aren't orphans, but at this stage it's just an impression," Jacques Hintzy told Radio Television Luxembourg.