MANAGUA, Nicaragua — Operating from this Sandinista sanctuary, the international kidnapers stalked their victims, documented their habits and calculated multimillion-dollar ransoms.

They followed one prominent Mexican businessman to a church Mass for his dead wife; they staked out the homes of others from nearby bus stops and parks. They knew the bank account numbers, quarterly earnings and favorite colors of Latin America's richest men and women.

"Ignacio Aranguren--he has a \o7 lot\f7 of money," the kidnapers observed of the Mexican food magnate. "Very much loved by his family. Would negotiate."

The ring, linked to at least six kidnaping cases, might have gone undetected had a huge and illegal arms depot belonging to Salvadoran guerrillas not exploded on the outskirts of Managua in May. Secreted along with guns and missiles were the kidnaping files as well as hundreds of passports, equipment for falsifying identification papers and guerrilla propaganda.

Now in the hands of a judge here and subject to the scrutiny of the FBI and police agencies from four countries, the stash revealed a vast kidnaping and weapons-smuggling network run by Latin revolutionaries for much of the last decade.

The staggering collection of documents provides a rare, panoramic look at the shadowy underworld of the radical left, the cooperative relationships among guerrilla organizations and their plots to raise money through ransoms and arms deals.

The network's tentacles reach far and wide, implicating Spanish Basque separatists, South and Central American Marxist groups and two convicted Canadian kidnapers languishing in a Brazilian prison.

It may also have ties to the World Trade Center bombing in New York, according to investigators.

"This is a real Pandora's box," said Judge Marta Quezada, who is in charge of the case.

Passports from almost two dozen countries were found, including several blank U.S. passports--a valuable commodity even in the most advanced terrorist circles.

People appear with multiple identities. One key figure, identified at one point as Julio Aguilar Cruz, turns up in six passports, each with a different name and a different nationality.

The discovery revived memories of the Sandinistas' recent past, when, as rulers of Nicaragua from 1979 to 1990, they converted the country into a haven for radical leftists from around the world. And it raised questions about the present: The arsenal and the network almost certainly could not have existed without the knowledge of Sandinista officials, diplomats say. They add that the network could still be active.