At 9:30 last Saturday morning, two FBI agents were lingering over breakfast in the Sheraton San Cristobal Hotel when they were suddenly summoned to the telephone.

Little more than an hour later, the agents found themselves en route to the United States aboard Ecuadorian Air Lines flight 052. A fellow passenger, put aboard the plane wearing a pair of Chilean handcuffs that will have to be returned by the FBI, was Michael V. Townley.

For days, Justice Department officials had been trying to get Chile to turn over Townley, a 35-year-old expatriate American and alleged Chilean secret police operative wanted for questioning in the 1976 Washington murder of exiled former Chilean diplomat Orlando Letelier.

Townley's abrupt expulsion - which dispensed with the due process guaranteed under Chilean law - was staged with such haste that both he and the FBI escort agents ended up leaving their luggage behind.

The deportation, informed pro-government sources said, reflected President Augusto Pinochet's eagerness to wind up the U.S. investigation of the Letelier affair, and end Chile's official involvement in an extremely disagreable situation.

Were Townley able to tie the murder directly to the highest levels of the Chilean government, the sources reasoned, he never would have been allowed to leave the country.

The government itself, however, has remained silent on the events of last Saturday - an indication that it may not yet consider itself out of the woods in the Letelier case.

Throughout the investigation - which early on implicated agents of DINA, Chile's now-dissolved secret police - Pinochet has pledged complete cooperation with U.S. authorities, and has repeatedly denied his government's involvement in the murder.

But while Pinochet last September, in Washington for the signing of the Panama Canal Treaty, kissed his thumb in a Catholic gesture and swore to a press conference that there was no government connection, his definition of the government has progressively narrowed.

Several weeks ago, after Townley, a U.S. citizen living in Chile, was identified as a person sought in the case and was tied to DINA, an official statement pointedly noted that "no Chilean citizen" was involved in the crime. Speaking to reporters last week, Pinochet said, "My own conscience is clear."

Most Chileans seem more than willing to believe that Pincohet himself had no direct knowledge of the murder of Letelier. But pressure from the investigation, informed sources says has already led to the officially unexplained resignation of Gen. Manuel Contreras from the Chilean Army.

The head of DINA at the time of the slaying, Contreras is known to be a close Pincochet associate. Before his March 21 resignation, he was often described as the second most powerful man in Chile.

Townley's expulsion, and the events leading to it, have raised more questions than they have answered in the 19-month-old case.

Although U.S. authorities reportedly believe that Townley had some connection with the murder and was acting under Chilean government orders, no evidence to support that belief has yet been made public.

What remains in the wake of Townley's expulsion is a tale of international intrigue and extremist violence, diplomatic tip-toeing and threats.

The Pinochet government also anxious hopes that Chile's cooperation in Letelier investigation will help it regain a position of respect in the international community.

The question of Chile's international image, severely tarnished by accusations of human rights abuses, brings the Letelier case full circle.

On Sept. 10, 1976, the Chilean military junta stripped the exiled Letelier of his citizenship, and accused him of organizing an international publicity campaign aimed at "the political, social and economic isolation" of Chile.

Letelier, one of the most outspoken of the thousands of Chileans who fled or were thrown out of the country following the 1973 military coup that toppled Marxist President Salvador Allende, was active in exile attempts to organize an international economic boycott of Chile.

Ten days after his citizenship was lifted Letelier and an associate were killed when a remote control bomb blew up his car at Sheridan Circle in Washington, near their office.

The repercussions from that explosion - which U.S. investigators suspect was set off by rightwing Cuban terrorists acting on instructions from DINA - probably made Chile more of an international pariah than any campaign Letelier might have organized.

The partial story of Michael Townely's involvement in the case - pieced together from accounts by diplomats and Chilean official sources - begins in the small South American country of Paraguay.

In July, 1976, approximately two months before Letelier's death, two men carrying official Chilean government passports asked for and were given diplomatic visas to the United States.

The names on the passports were Juan William Rose and Alejandro Romeral Jara.#TWithin the next several days, before the men had left Paraguay, the visas were revoked when U.S. Embassy officials began to wonder why Chilean officials were applying for visas in a third country.

The men were suspected of being Chilean intelligence agents, and the photographs submitted with their visa applications were retained and sent to Washington to include in the government's files on DINA.

Last summer, sources here said, Cuban exile informants combing U.S.-supplied photos of suspected DINA agents picked out those photographs, and identified at least one of them as a man who had met with rightwing Cubans in the United States immediately before Letelier's murder.

What at first seemed like the answer to the question of how the two entered the United States - after being refused visas in Paraguay - was supplied by the U.S. Embassy in Santiago. It reported granting visas to two officials named Romeral and Williams in August, 1976 - one month after the Paraguayan incident and a month before Letelier's death.

In late 1977, the FBI began pressing the Chilean police for information on Romeral and Williams. Months passed.

Finally in February, in the face of continued Chilean Stonwalling, Justice Department investigators decided to go public with some of the information they had. Through diplomatic channels, in a court-to-court procedure called "letters rogatory," they directed a list of 53 questions to the two Chilean officials, and asked the Pinochet government to produce them.

The photos that had been attached to the passport applications filed in Paraguay were also leaked to the press, and published both in Washington and here.

The men in the pictures were quickly identified by friends and relations as Armando Fernandez Larios, a Chilean Army captain attached to DINA, and Townley, a U.S. citizen living in Chile with a history of involvement in right-wing political activities.

An electrician who had moved to Santiago with his family in 1977, Townley had been involved in militant anti-Allende activities. In 1973, he allegedlp participated in an anti-Allende commando operation in the port city of Conception in which a night watchman was killed.

Townley left for the United States after the Concepcion incident, according to his wife and attorney, who say he returned to work ofr DINA after the military takeover. His missions for KINA, they said, required frequent trips to the United States.

After initially denying the existence of the Chillean officials who had applied for U.S. visas as Romeral and Williams, the government in mid-March produced in court two men who it said had traveled to the U.S. in 1976 on visas bearing those names.

A surprised U.S.-appointed Chilean attorney, however, refused to question the two on grounds that they bore no resemblance to the visa photographs identified by the Cubans.

At this point, sources here said, it became clear that contrary to what U.S. investigators had assumed, two sets of Chilean agents had applied for visas in 1976 using false names of Romeral and Williams.

The second set, who had obtained their visas at the U.S. embassy in Santiago had apparently traveled to the United States on a separate DINA misssion that has not been tied to the Letelier case.

According to sources close to the investigation, U.S. investigators believe Townley traveled to the United States on his own or another American passport.

Going largely on the press reports about Townley and Fernandez, angry U.S. officials said they were the wanted men - and demanded that Chile produce them.

Following a number of bitter exchanges between U.S. and Chilean officials, Townley and Fernandez, who had allegedly disappeared following their identification in the press, were finally produced.

Townley was brought before a military investigator where he was interrogated in secret for 18 hours before appearing in court with Fernandez.

Fernandez reportedly answered all questions directed to him during the closed court proceedings, and was, for the moment at least, eliminated from U.S. interest. Townley, speaking only in Spanish, reportedly refused to answer any questions, invoking the U.S. 5th Amendment.

It took the Chileans a week to decide to hand Townley over for further questioning in the United States - a decision marking the first time a DINA operative has been exposed to any sort of scrutiny outside Chilean secret police circles.

Informed observers say Chile's belated cooperation demonstrates both the country's and Pinochet's lack of options in the face of mounting internal and foreign pressures.

Faced with the prospect that refusal to turn over Townley would be viewed by the world community as tantamount to an admission of complicity in the Letelier slayings, Chile apparently felt it had little choice.