Postscript : A New Theory on ’84 Bomb Mystery : Argentine mercenary linked to Sandinistas is suspected in attack on Contra leader’s news conference 10 years ago.

Ten years ago, a group of Costa Rican and American journalists ventured into the night, bound for a secret rendezvous with guerrilla leader Eden Pastora.

As the news conference began in a jungle hide-out in southern Nicaragua, a bomb intended for Pastora shattered the room, killing an American journalist, two Costa Rican colleagues and a number of Pastora’s aides. Pastora, the fabled Comandante Zero of the revolution that ousted Nicaraguan dictator Anastasio Somoza, was gravely wounded but survived.

The bombing at La Penca became one of the most notorious and mysterious incidents of the long war between Nicaragua’s Sandinista regime and U.S.-backed Contra rebels, who by that time included Pastora. Suspects were plentiful but evidence scant. Most accusers blamed the CIA, and the Costa Rican government indicted two CIA operatives.

Now, a decade later, a new explanation has emerged.

A Costa Rican congressional commission, concluding a 3 1/2-year-long investigation, blamed the bombing on an Argentine terrorist who operated in Nicaragua under the 1979-1990 Sandinista regime. The orders to assassinate Pastora came from deep within the Sandinista Interior Ministry, said Sonia Rodriguez, president of the commission.

“The attack at La Penca is the maximum revelation of the desire to eliminate Eden Pastora, and although there existed other groups that considered Pastora an obstacle to their interests, it is clear that the person who executed the act was intimately tied to a section of the Sandinista Front government,” the commission said in a 200-page report.

Some pieces of the La Penca puzzle were known within days of the May 30, 1984, explosion. The bomb had been placed inside a camera bag and smuggled into the news conference by a man posing as a Danish journalist named Per Anker Hansen. The last television footage taken by a Costa Rican cameraman who was killed in the explosion, Jorge Quiros, showed “Hansen” sneaking out of the hut where the news conference was taking place seconds before the bomb was triggered by remote control.

Hansen feigned injuries himself and then vanished after he and 20 badly injured journalists were evacuated from the jungle.

During the years that followed, survivors, journalists and other investigators chased down numerous leads in a quest to find out who Hansen was and who he was working for.

Pastora, the flamboyant guerrilla fighter, had plenty of enemies to choose from. He had betrayed his Sandinista comrades. He spooked the CIA, which considered him unreliable. He resisted the U.S. government’s grand scheme of uniting Pastora’s rebel front in southern Nicaragua with Contras in the north.

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But all efforts to close this chapter of dirty tricks failed. Finally, new information emerged that pointed investigators in the direction of the Sandinistas.

Using recently discovered fingerprints, the Costa Rican commission identified the bomber as Vital Roberto Ganguine, a member of the leftist Argentine People’s Revolutionary Army, which allied with the Sandinistas in the 1970s.

Ganguine, along with other revolutionaries from all over Latin America, worked for a shadowy intelligence and espionage unit within the Sandinista Interior Ministry. Investigators matched a fingerprint from official Argentine records with those on Hansen’s immigration documents for Panama to prove that Hansen was Ganguine.

The Costa Rican investigation largely confirmed the results of a multinational probe conducted last year by the Miami Herald and a group of Argentine journalists and U.S. free-lance reporter Douglas Vaughan, who is credited with turning up the Panamanian immigration documents.

Vaughan at one time worked as an investigator for the Christic Institute in its $23-million lawsuit that accused 28 Contras, CIA operatives and others of conspiracy in the La Penca bombing. The plaintiffs were Tony Avirgan, a television cameraman who was wounded in the bombing, and his wife, Martha Honey, for whom proving CIA involvement became a crusade in the years after the bombing. A federal judge threw out the suit in 1988, saying it was frivolous, and ordered the plaintiffs to pay court fees.

Both the Costa Rican commission and the Herald reported that Ganguine was said to have been killed in a 1989 Argentine guerrilla attack on the La Tablada army barracks near Buenos Aires. But the Costa Rican investigators said Ganguine’s body was never identified, and an arrest order remains in effect in Argentina.

The Sandinista Front, which governed Nicaragua from its overthrow of Somoza in 1979 until its upset loss in 1990 presidential elections, denied the reports that it was involved in the La Penca bombing. Otherwise, the news surprisingly has had little impact in Managua--in part because Pastora’s profile has been eclipsed by time, and partly because the Sandinista Front is caught up in more immediate crises and more recent scandals.

“Maybe it’s just old news,” a diplomat in Managua said. “Eden Pastora isn’t that important anymore. The judgment now is what dirt can you get on your enemies today.”

Among the survivors whose lives were shattered 10 years ago, there is mixed reaction.

In her new book, “Hostile Acts: U.S. Policy in Costa Rica in the 1980s,” Honey indicates that she and Avirgan believe the bomber was Ganguine. They investigated the new information themselves and were able to place “Hansen” in Sandinista Nicaragua.

But some of the other survivors remain convinced of CIA involvement. They argue that if the Sandinistas were responsible, the U.S. government, eager throughout the 1980s to publicize any and all negative news on the leftist Nicaraguan regime, would have made sure the story got out before now. Since that didn’t happen, these survivors conclude, Ganguine was not the man.