The retired U.S. Marine at the center of an espionage investigation at the FBI and White House traveled to the Philippines numerous times during the period in which he allegedly passed sensitive U.S. documents to opposition leaders here, official records show.

Leandro Aragoncillo, a naturalized U.S. citizen charged with stealing more than 100 documents from the FBI, visited his home country 15 times from 2000 to 2005, usually staying about two weeks or less, Philippine Bureau of Immigration records show.

In addition, Philippine and U.S. authorities say that a former national police official also charged in the case, Michael Ray Aquino, had a valid Philippine passport and U.S. tourist visa when he entered the United States in July 2001 -- despite being charged by Filipino authorities in cases involving allegations of murder, kidnapping and drug trafficking.

U.S. immigration and law enforcement officials said Friday that the Philippines never issued an extradition request or placed Aquino on a watch list, which could have prevented his entry into the country. The U.S. Immigration and Customs Enforcement agency eventually opened a criminal investigation after Aquino applied for legal residency last year, officials said.

U.S. authorities declined Friday to say why they were unaware of Aragoncillo and Aquino's alleged spying until Aragoncillo drew their attention by attempting to intervene after Aquino was arrested for overstaying his visa. The subsequent investigation has raised the possibility that Aragoncillo pilfered classified documents while working as a security official in Vice President Cheney's office and has shaken the Philippine political establishment.

Aragoncillo and Aquino are charged in the theft of more than 100 documents, including several dozen marked top secret, during Aragoncillo's stint as an FBI intelligence analyst at Fort Monmouth, N.J., earlier this year.

In Washington on Friday, FBI counterespionage agents continued to examine computer files, hard-drives and other items and interview staffers at Cheney's office to try to assess the damage, sources said. Aragoncillo is cooperating with authorities and, according to an ABC News report, has admitted to taking files while working under Cheney from 2001 to early 2002.

Former Philippine president Joseph Estrada and Sen. Panfilo "Ping" Lacson have admitted in interviews with The Washington Post and other news organizations that they received U.S. documents from Aragoncillo, but both have played down the information as gossip or routine political analysis. A U.S. law enforcement official confirmed Friday that Estrada is one of three current or former Philippine officials referred to anonymously in federal court documents filed in New Jersey.

Justice Secretary Raul Gonzalez said Friday that Estrada and Lacson also may have financed Aragoncillo and Aquino's activities. If that is proven, Gonzalez said, they could be charged in the Philippines for sedition.

"There are persistent reports that Leandro Aragoncillo has been paid by some popular personalities here in this country," said Ricardo Diaz, chief of the Interpol division of the National Bureau of Investigation. "We would like to investigate whether there are bases or evidence to prove these reports."

Diaz said Philippine investigators so far have no independent information about whether money was exchanged, adding that they will rely in part on details provided by U.S. authorities.

U.S. officials have confirmed that Aragoncillo was paid for information but have yet to disclose how large a sum he received. The criminal complaint filed against Aragoncillo in Newark last month depicts him as enthusiastically participating in the alleged spy plot, motivated, at least partly, by a personal interest in promoting political change in the Philippines.

Aragoncillo, a 21-year veteran of the U.S. Marine Corps, worked under both Cheney and Al Gore as an administrative chief in the security detail from July 1999 to February 2002, according to the Pentagon. Two law enforcement officials said Friday that the focus of the investigation is on Aragoncillo's time under Cheney.

An FBI official said Aragoncillo underwent a polygraph examination to take the job at the bureau, as required under reforms passed after the Robert Hanssen spy scandal.

The official said the hiring process was handled routinely, but said that Aragoncillo's service at the White House certainly would have helped him get the job. "The fact that you already had the clearance and that you worked [at the White House] and are a Marine -- those are all good bona fides," the official said.

Officials with the Philippine consulate in New York said that Aquino's passport was canceled in August 2001, after he had entered the United States. A new passport was issued for Aquino in September 2004, officials said.

In October 2004, Aquino applied for a green card, which would give him legal residence in the United States, an ICE spokesman said. Aquino was denied because of his connection with possible criminal charges in the Philippines and, in March 2005, he was arrested for overstaying his visa.

That arrest eventually led to the unraveling of the alleged espionage effort. Aragoncillo, identifying himself as an FBI employee, called immigration authorities to ask about Aquino's case. The FBI was notified and launched an audit that revealed that Aragoncillo allegedly had gained unauthorized access to documents involving the Philippines, according to the criminal complaint.

Eggen reported from Washington.

Leandro Aragoncillo went to his home country 15 times.