Six French nationals held in Chad over an alleged attempt to fly 103 children out of the country have gone on hunger strike, a judicial source says.
The children have been temporarily placed in a Chadian orphanage
The six members of the Zoe's Ark charity began the strike because of concerns over how the legal process was conducted, the source said.
They also feel they have been let down by the French government.
The charity workers are being held in Chad's capital, N'Djamena, on charges of kidnapping and fraud.
"They have been on hunger strike since last night (Friday)," the legal source told the BBC's Stephanie Hancock, adding that they were refusing food but were drinking water.
The source also said that the trial of the charity workers would start in the coming weeks in Chad - this has not been confirmed by N'Djamena.
Meanwhile, a lawyer for the detained workers said in France he was optimistic that French President Nicolas Sarkozy would intervene on their behalf, the AFP news agency reported.
Last month, Mr Sarkozy flew to Chad to discuss the case with Chadian officials, and N'Djamena later released 11 European nationals who had been arrested together with the six French workers.
The Zoe's Ark members were arrested in October for what Chadian officials say was an illegal attempt to fly 103 children, aged one to 10, to France.
Zoe's Ark has said it thought the children were orphans from the conflict-torn region of Darfur in neighbouring Sudan.
Stephanie Lefebvre, secretary-general of Zoe's Ark, has insisted the charity was acting out of compassion.
But international humanitarian organisations have said that almost all the children were from Chadian villages in the border area, and have at least one parent or adult guardian, according to the AFP news agency.
Chadian President Idriss Deby has described the operation as "inhumane" and "unacceptable" and said those responsible would be "severely punished".
French government sources told the BBC that some 300 families in Europe may have paid a total of up to 1m euros ($1.4m) to charities in the hope of being able to adopt one of the children arriving from Chad.
Most of these families were French, and the remainder Belgian.
The UN children's agency, Unicef, said the operation "took place in violation of international rules".
In August, the French authorities issued a warning about the activities of Zoe's Ark, saying there was no guarantee that the children whom the group wanted to transport were actually orphans.