MANAGUA, NICARAGUA -- For Rosa Moreira Trana, the events of May 12 were all too familiar. Armed agents of the Sandinista state security police arrived at the ramshackle shanty of the 58-year-old widow and took her away, they said, for "questioning," along with a pregnant daughter, Maria Ignacia.

The arrests came three days after the two had been interviewed by The Washington Post for an article on human rights under Nicaragua's Sandinista government.

At that time, they were in their third week of "house arrest" in Tipitapa, 13 miles east of Managua. Before that, they had been held more than two weeks in the capital's El Chipote prison, officially an "operations center" of the General Directorate of State Security, the Sandinista secret police.

Moreira, her 23-year-old daughter and two sons had been arrested in early April on suspicion of involvement with the Nicaraguan contra rebels, a charge they deny. For Moreira, it was the fourth time she had been arrested on state security charges since September 1980.

In the interview, Moreira had described suffering psychological torture in El Chipote, including deprivation of sleep and death threats against her children. Sobbing, the frail grandmother had said she was held in a tiny, stifling, lice-infested cell with no light and only a hole in the ceiling to let in air. She said she was released that time after signing a confession that she was not allowed to read.

Moreira said she believed her family had come under Sandinista suspicion because they hailed from a southern province where the contras have support. She said the Sandinistas suspected -- wrongly, she insisted -- that her sons had been members of the National Guard under former ruler Anastasio Somoza.

According to another of Moreira's 12 children, Teresa, 33, the agents who arrested her mother and sister the next time "said they were going to question them and then bring them back to the house, but they haven't brought them back yet." Instead, Teresa said in an interview Aug. 15, her mother and sister were taken to the Zona Franca prison, joining her two brothers, Lorenzo, 37, and Marcial, 26.

Then, a few days before a regularly scheduled visit to the prison by the International Committee of the Red Cross in July, the two women were moved to the Modelo Prison in Tipitapa, ostensibly to take a sewing course, Teresa said.

Another sister, Marta, 30, said Maria Ignacia, who has two young children, was ill in her seventh month of a third pregnancy. Marta said her mother had suffered what appeared to be a mild stroke, which left her face and left arm paralyzed.

The arrests of Rosa Moreira and her children have disrupted an impoverished family of the kind the Sandinistas say they fought their revolution for. Yet circumstances have made the family bitter opponents of the Sandinista government and plunged them into a nightmare of seemingly arbitrary arrest, suffering and uncertainty.

Although thousands of other suspected contras or sympathizers have suffered similar fates, the Moreiras' case stands out in that the mother and two of the children, Maria Ignacia and Marcial, were born in Costa Rica. Although they have lived for years in Nicaragua, they have Costa Rican nationality, and their case has come to the attention of Nicaragua's southern neighbor.

Costa Rican Ambassador Farid Avales Esna said Friday he had appealed directly to Interior Minister Tomas Borge for the release of the two women, but had not received a response.

The president of Costa Rica, Oscar Arias, was the driving force behind a Central American peace plan aimed at ending conflicts in the region. The plan calls for an end to Nicaragua's state of emergency and the freeing of political prisoners, among other provisions to take effect Nov. 7.

So far, the peace plan has not helped Teresa and Marta Moreira, who spend their days working for the release of their mother, sister and brothers.

Wearing torn and soiled clothes and with five children in tow, they have regularly made the rounds of the Red Cross, the nongovernmental Permanent Commission for Human Rights, the Costa Rican Embassy and a committee of relatives of political prisoners, defying what they said were warnings from the Sandinista state security directorate not to get involved in opposition human rights activities.

The reason for the detention of Rosa Moreira and Maria Ignacia on May 12 is still unclear. "It's a mystery why they were arrested," said an official of the International Committee of the Red Cross.

The head of the Permanent Commission on Human Rights, Lino Hernandez, said he believed the arrests of the mother and daughter, who he said had been under "permanent surveillance," came in "reprisal" for their talking to a reporter on May 9. Hernandez himself has now been arrested and summarily sentenced to 30 days in jail on charges of "disturbing public order." The arrest occurred when police and Sandinista youths broke up an opposition political demonstration that he was observing, witnesses said.

Teresa and Marta Moreira said, however, that the agents who arrested their mother and sister made no mention of the interview. They said the arrests came the same day that their brothers were transferred from El Chipote prison, where they had spent more than a month in detention, to the Zona Franca penitentiary.

The sisters said the Sandinistas had accused their mother of being a contra from the "southern zone" and suspected Maria Ignacia of serving as a contra courier and of being the wife of a contra commander code-named Puma. Marta said, "We don't know any Puma, and none of us is with the contras."

According to Sister Mary Hartman, a pro-Sandinista American nun from Wisconsin who has lived in Nicaragua for 25 years and now works for the government's National Commission for the Protection and Promotion of Human Rights, the two may have been arrested "simply because they were people who were organizing the other women" in the opposition committee of relatives of political prisoners. She charged that this group was being funded by the United States and insisted, contrary to the committee's assertions, that "there is absolutely no torturing going on" in Sandinista jails.

"As in the case of a country at war, you cannot collaborate with the CIA, the U.S. Embassy and with people who are supporting the contras," Hartman said of the arrests.