"This information is among the rumours circulating around the Zoe's Ark affair. It is without foundation," she said.
Zoe's Ark is a French charity which has been accused of abducting children from Chad, but the organisation has said it has been conducting "child rescue" operations from Sudan's restive Darfur region.
Six French Zoe's Ark workers have been charged in Chad with the kidnap and plan to send 103 other children they claimed were orphans from Darfur on a plane to France.
They face up to 20 years at hard labour in Chad if convicted.
Various non-governmental organisations, including UN agencies, have since cast doubts on whether the children were from Darfur, or indeed orphans.
While Zoe's Ark says its intentions were purely humanitarian, UN and other aid agencies say taking children - even those in desperate circumstances - away from their families and culture may not be the best way to help them.
The affair also has focused attention on the inability of many African governments to safeguard children and ensure that those claiming to want to help are not sex or labour traffickers.
Kagah said that the network of human rights associations in Chad gathered the information about the 74 children after several parents went to inform the organisation their children were missing.
|Zoe's Ark members could serve up to 20 years|
of hard labour in Chad if found guilty [AFP]
The children "have effectively been kidnapped. They landed at this military airport to go to an unknown destination," Kagah said.
Kagah, who received the letter on Tuesday said he would initiate an investigation.
The children are aged between one and six, according to the letter that Kagah received.
"We do not know how many [other] children were transported in such conditions," Kagah said.
The human rights groups said the plane carrying the children landed at a base known as Mourmelon on September 17.
But Captain Christophe Prazuck, a French military spokesman in Paris, said the base had only a 950-metre strip of grass normally used for practice by parachutists.
"On September 17, which is the supposed date [of the flight], there was no trace of aerial movement on this 950 metre-long strip of grass," he said.
Christophe Letien, a spokesman for Zoe's Ark, said he knew nothing about the report and that his group was not involved.
"I can assure that this was not from Zoe's Ark. That is absolutely certain. Just one aircraft was chartered and it is the plane that is still there at Abeche," he said.
"As for other organisations that might have done this type of thing, I know absolutely nothing."
Nicolas Sarkozy, the French president, sparked anger in Chad when he suggested earlier this week that he would bring the detained French charity workers back to France.
Outside the court in which the six Zoe's Ark workers were being heard, in Chad's capital city of N'Djamena, around 100 protesters gathered with a banner that read "Sarkozy, justice must be done in Chad."
A statement from Sarkozy's office said that "the president of the republic is delighted with the co-operation under way between the Chadian legal system and the French legal system."
Sarkozy "expressed his confidence in the legal system and underscored that it must work in a calm manner and in the full respect of Chadian sovereignty".
The French president reiterated that "French authorities have provided, since the beginning of the affair, consular, medical and material assistance" to those detained, the statement said.
Zoe's Ark has insisted throughout the case that its sole aim was a child rescue operation to save war orphans from neighbouring Darfur.