CARACAS, VENEZUELA - Venezuelan authorities released four members of a nonprofit group who were detained Friday while trying to transport at least 120 Venezuelan children to Peru for reunification with their parents.

Authorities grounded a charter flight Friday from Simon Bolivar International Airport, claiming that nine children's travel documents had been falsified. All the children were returned to relatives in Venezuela, officials said.

The flight was organized and financed by the Venezuelan Union in Peru, founded by exiled political leader Oscar Perez. His wife, Marta Molina, was among the four detainees. They were held on suspicion of involvement in falsifying travel documents.

The incident was being investigated as possibly linked to trafficking of minors, Venezuela's attorney general, Tarek William Saab, said in a Twitter post Saturday.

1) El día de ayer fuimos informados de la inédita acción: sin precedentes en nuestra historia republicana; de fletar con destino a Perú y a través de una presunta e indocumentada Ong: un vuelo charter a bordo de 120 niños con poderes y permisos de viaje fraudulentos #DDHH — Tarek William Saab (@TarekWiliamSaab) December 16, 2017

Juan Gonzalez, an attorney for the Venezuelan Union, flatly rejected the accusations. "No criminal wrong has been committed here," he said.

The Venezuelan Union claimed that Venezuelan authorities acted "arbitrarily and without legal justification" and insisted that all the children had appropriate permits to travel to their parents, who left the country because of its economic crisis. The Union suggested the youngsters were being used as political pawns.

"Most of the children who were on this flight are sick children — children with cancer or Down syndrome," a woman who identified herself as Anmarie told VOA at the airport Saturday.

Anmarie said she had planned to take the flight to Lima with four of her grandchildren; it was not clear whether any of them had a health issue.

"We had to travel out of necessity," Anmarie said, because in Venezuela "there are no medicines for these children."

Medicine and other staples have become increasingly rare and costly in Venezuela's protracted political and economic crises.