A new chapter in the Central American arms traffic story opened this week when Costa Rican officials said they had uncovered a group of revolutionaries who were running guns overland from Costa Rica to El Salvador.
Their announcement confirmed popular suspicions here that Salvadoran rebels had taken advantage of Costa Rica's black market in armaments. But what surprised Costa Ricans was that this was an overland operation.
The discovery of the group and its huge weapons arsenal stunned investigators , who hit upon the stash when they raided a house in San Jose in search of an Iranian kidnap victim.
They discovered seven startled houseguests and the largest illegal weapons find in Costa Rica's recent history, valued at an estimated $200,000.
''This is the first concrete proof that arms traffic exists between Costa Rica and El Salvador,'' noted one judicial official.
The house held about 150 firearms, as well as cardboard boxes stuffed with thousands of rounds of ammunition, grenades and grenade launchers, 500 combat uniforms, chemicals for fabricating bombs, communication devices, and equipment for falsifying documents.
Most of the weapons were of American and West European manufacture, according to officials who did not specify whether any of them were from Soviet-bloc countries.
The seven arrested included persons of Argentine, Costa Rican, Salvadoran, and Nicaraguan nationality.
According to judicial police, the group ran arms to the Salvadoran guerrilla coalition known as the Farabundo Marti National Liberation Front.
''The cars went constantly,'' notes Manuel Molino, chief of investigators of the Judicial Investigation Organization, which uncovered the operation.
''We asked the leader why they didn't just buy and send the arms from Nicaragua,'' said Molino. ''He told us that there was too much vigilance and that it is easier to do it in Costa Rica. He said there is 'a lot of corruption here.' ''
Security officials admit that the weapons may be left over from l978-79, when Costa Rica was a stopping ground for planes laden with weapons for Nicaragua.
The judicial detectives, who also discovered a plan for hiding weapons in small aircraft, do not discard the possibility that air trafficking may also exist. Residents of northern Costa Rica have long complained that planes loaded with arms take off from isolated beach airstrips.
A congressional comittee was formed in July l980, after a Panamanian plane loaded with ammunition crashed outside of San Salvador after loading in Costa Rica. The pilot told authorities he had picked up the munitions in Costa Rica.
Last October the committee censored Costa Rican President Rodrigo Carazo Odio and several security officials who came under fire for permitting arms to be shipped to Sandinistas in Nicaragua.