Two envoys dispatched to seek the release of President Jose Napoleon Duarte's kidnaped daughter returned empty-handed today, saying they were turned down in attempts to meet Salvadoran rebel leaders based in Mexico.

"I was not able to talk with anyone," said Communications and Culture Minister Julio Rey Prendes on his arrival from the Mexican capital.

Rey Prendes, Duarte's longtime adviser and friend, flew secretly to Mexico on Sunday with Deputy Foreign Minister Ricardo Acevedo. Rey Prendes said they sought to enlist help from the rebel movement's political wing, the Democratic Revolutionary Front, in securing the release of Ines Guadalupe Duarte Duran, the president's 35-year-old daughter abducted here a week ago.

"I wanted to talk to them to see if they could influence the FMLN," he explained, using the Spanish acronym for the umbrella rebel military alliance, the Farabundo Marti National Liberation Front. "I had to try to find out about whether there was a connection."

Salvadoran and diplomatic sources have said callers identifying themselves as part of the Pedro Pablo Castillo Front contacted the government during the weekend demanding release of rebel prisoners in return for the safe return of Duarte's daughter. The rebels' official Radio Venceremos announced the creation of the front July 14, saying it was dedicated to the 450 political prisoners held by Duarte's U.S-backed government.

A ranking Salvadoran intelligence official said that, despite the weekend contacts, the government remained unsure who the captors were. From their demands and identification, however, officials have concluded that the kidnapers are connected to one of the five guerrilla groups in the Farabundo Marti National Liberation Front.

Against that background, Rey Prendes said, he went to Mexico to see rebel political officials in the hope they could help arrange negotiations with guerrilla leaders leading to release of Duarte's daughter. Government officials have expressed the belief that she is being held by extremist members of one of the insurgency's military groups, which have in the past taken stands sharply different from the political leadership's.

The Democratic Revolutionary Front, FDR by its Spanish initials, denied yesterday that it had anything to do with the abduction or knowledge of who had carried it out. Hector Oqueli, an FDR official in Mexico City, said for that reason front officials would not be meeting with Duarte's envoys.

Rey Prendes said, however, that he had obtained agreement for such a meeting from "someone in Oqueli's office" before his departure. He declared on his return today that news leaks of his mission might have caused the FDR to change its mind.

Oqueli charged that the trip to Mexico and its disclosure by Salvadoran government sources could have been an effort by Duarte to pressure FDR leaders into getting involved in the abduction crisis by focusing attention on them.