By GINGER THOMPSON

GUATEMALA CITY, Nov. 20 - The reams and reams of mildewed police documents, tied in messy bundles and stacked from floor to ceiling, look on first sight like a giant trash heap. But human rights investigators are calling it a treasure hidden in plain sight.

In Guatemala, a nation still groping for the whole truth about decades of state-sponsored kidnapping and killing, the documents promise a trove of new evidence for the victims, and perhaps the last best hope for some degree of justice.

Last summer, authorities from the Guatemalan human rights ombudsman's office, searching a munitions depot here, discovered what appear to be all the files of the National Police, an agency so inextricably linked to human rights abuses during this country's 36-year civil conflict that it was disbanded as part of the peace accords signed in 1996.

At that time, President Álvaro Arzú's government, struggling to usher this country through an uncertain transition from war to peace, denied to a truth commission that police files existed. It now seems clear, human rights investigators say, that Mr. Arzú's government, as well as those that followed, knew about the files all along.

In the months since the files were discovered, archivists kept them closed to the public and much of the news media because of concerns that, given the depot's many open, unfinished windows and doorways, the files could be pilfered or destroyed. In addition, the archivists said they needed time simply to do a preliminary examination to get a sense of what was in the files.

Following repeated requests, the ombudsman's office agreed to allow The New York Times to visit the files last week, after a rudimentary security system had been installed and archivists had begun taking samples of documents from the files.

Walking into some of the chambers is like staring down a tidal wave. Documents bundled as thick as bibles stand more than 10 feet tall in bat-infested rooms as dank and dark as caves.

There are buckets in every corner that attendants, dressed in rubber gloves and gas masks to protect against the fumes, have been using to catch leaks from the roof.

Everything seems to be there: from traffic tickets, driver's license applications and personnel files, to spy logs and interrogation records. There are hundreds of rolls of film and videos, along with snapshots of unidentified bodies, detainees and informants. Some of the files seem to have gotten slightly more careful treatment and were tossed into file cabinets marked "disappeared," "assassins" and "special cases."

There are transcripts of radio communications and stacks of arrest records listing "Communist" as the reason for arrest.

Sergio Morales, the head of the ombudsman's office, has previously told Guatemalan reporters that the archive also contains lists of children kidnapped from suspected guerrillas, along with the names of the families who agreed to take them in.

What remains unclear, investigators said, was why officials in Guatemala's prior governments - particularly the police - did not destroy the files, even though they appear to hold evidence of egregious abuses. Now that the archive has been found, almost 10 years after the end of the fighting that left at least 200,000 people dead, a new government, struggling to consolidate a fledgling peace, is still grappling with how to proceed.

"This presents a serious challenge for the government because there are going to be a lot of powerful names coming out of the files, and the justice system is very weak," Frank LaRue, director of the Presidential Commission on Human Rights, said in an interview. "But the government remains committed to opening the archive, and prosecuting people responsible for crimes."

Later he toned down his statement, saying, "I am not sure everyone in the government would agree with that."

It is not the first batch of government documents uncovered since the end of the war. Kate Doyle, director of the Guatemala Project at the National Security Archive, a nonprofit group based in Washington, pointed out that last year the government quietly opened the files of the former presidential intelligence agency, which was also accused of systematic human rights abuses and ordered disbanded. And in 1999, an activities log for a secret military unit responsible for kidnapping and killing government opponents was smuggled out of the military's files.

But the intelligence agency files had been ransacked before human rights investigators could get to them. The National Police files - mildewy and messy, but still intact - promise the most complete accounting of the government's campaign against people suspected of being leftists, a campaign initiated with money and advice from a succession of United States administrations worried about the spread of Communism.

As a precondition for opening the files to viewing by The Times last week, the lead investigator for the ombudsman's office, Gustavo Meoño, asked that specific details from documents describing extrajudicial kidnappings and killings, including names of victims and police officers, not be published.

"We have to act very carefully with this archive," Mr. Meoño said. "We do not want to unduly raise the expectations of the victims. And, for our safety, and for the safety of the files, we don't want to unduly frighten the people who are identified as perpetrators."

The ombudsman's office said it inadvertently found the archive in the munitions depot, not far from the center of the capital during a safety inspection prompted by complaints from neighbors that explosives were being improperly stored at the site. The neighbors did not know the half of it.

The files, in various stages of decay, date back more than a century and contain enough documents to stretch the length of 130 football fields.

Ms. Doyle said it is the largest discovery of secret government documents in Latin America. Michael McClintock, a Guatemala expert at Human Rights First, a New York-based nonprofit group, called the archive "the mother lode" during his visit here last week.

Mr. Meoño said there were files that referred to well-known cases, including the 1990 assassination of Myrna Mack, an anthropologist. He said a team of Belgian lawyers investigating the 1980 assassination of Walter Voordeckers, a Belgian priest, and the 1982 disappearance of Serge Berten, another Belgian citizen, found files on those cases during a visit to Guatemala in September, and had the government subpoena the former chief of the national police, Germán Chupina, for the first time since the end of the war.

"I show you these," Mr. Meoño said, referring to documents from the archives, "to make clear to you that we have great hopes that this archive is going to clear up mysteries that have tormented this country for decades."

That seemed to be clear to the directors of archival projects around the world, including those of Iraq, Cambodia, and Serbia, who also visited the police files here last week. The question that ran through many of their minds here, they said, was the same one that ran through their minds when they first examined damning files kept by governments led by dictators like Saddam Hussein and organizations like the Khmer Rouge: Why didn't the government destroy the files when it had the chance?

But Hassan Mneimneh, of the Iraq Memory Foundation, was not surprised that the files had been left alone. "Ultimately these files are the institutional memory of the bureaucracy," he said. "To expect a bureaucracy to destroy its files is to expect it to commit suicide."

Heriberto Cifuentes, a Guatemalan historian who was among the first outsiders to lay eyes on the files, said the fact that the government did not destroy them reflected a simple fact of Guatemalan life.

"Impunity reigns in Guatemala," he said. "So whether there are documents or not, people responsible for crimes do not expect to pay for them. They have always enjoyed blanket immunity."