MEXICO CITY, JUNE 25 -- The case of a murdered journalist has reopened a murky chapter in Mexico's recent past, exposing a tale of corruption, drug trafficking, larceny and assassination by former members of the country's feared secret police force. The revelations appear to have sparked a housecleaning in the Mexico City police department, which became a repository for discredited agents of the former Federal Security Directorate when President Carlos Salinas de Gortari took office six months ago. But it is unclear whether the apparent purge will satisfy growing public demands for a shake-up in the capital's security forces and greater accountability for past abuses. In fact, some analysts say, the disclosures in the case of murdered political columnist Manuel Buendia may have opened a Pandora's box for the Salinas administration, as commentators and opposition politicians demand an investigation of the role of top government officials, including at least one current cabinet minister. The revelations also have ignited demands in the Federal District Assembly for the abolition of the Intelligence Directorate that was created within the Mexico City police department in December and that has been accused of human rights violations. In the latest development in the Buendia case, authorities announced Friday the detention of at least three more former officers of the Federal Security Directorate, known as the DFS, in connection with the May 1984 murder of Mexico's best-known columnist. The secret police unit, an arm of the powerful Interior Secretariat, was disbanded in 1985 amid allegations of rampant corruption in its ranks. On June 13, police arrested the 47-year-old former director of the DFS, Jose Antonio Zorrilla Perez, charging him with ordering Buendia's assassination and a subsequent coverup as part of a plan called "Operation News." Government investigators charge that the murder was aimed at heading off a Buendia expose of Zorrilla's links to top drug traffickers. Authorities are also investigating those links, including alleged payments to Zorrilla by drug kingpin Rafael Caro Quintero and other traffickers in return for protection and DFS credentials. Zorrilla has denied the charges, calling the Buendia case "a problem of public opinion." A week after Zorrilla's arrest, police captured Juan Rafael Mora Avila, 36, a former DFS agent and sometime rock musician and movie actor. He was accused of being a "material author" of the slaying of Buendia, who was shot in the back on a downtown Mexico City street. Mora Avila, a grandnephew of former Mexican president Manuel Avila Camacho, insisted at a pretrial hearing that the actual triggerman was another DFS agent, Jose Luis Ochoa Alonso. Mora Avila initially testified Wednesday that he drove a getaway motorcycle for Ochoa, but later changed his story. He has been charged as an accessory to murder in the case. According to a report by the Mexico City attorney general's office, Ochoa himself was gunned down in a telephone booth six weeks after the Buendia killing in order to silence him. Another murder, that of an Interior Secretariat official in 1985, may also be linked to the Buendia case, newspapers reported today. Currently in custody, besides Zorrilla and Mora Avila, are former DFS officers Juventino Prado Hurtado, Raul Perez Carmona and Sofia Naya, an attorney general's office spokesman said. At least two other persons reportedly are being sought in the Buendia case. Prado, Perez Carmona and Naya held posts in the controversial new police Intelligence Directorate up to the time of their arrests last week, authorities said. They were associates of Miguel Nazar Haro, who was named chief of the Intelligence Directorate in December but was forced to resign in February amid charges that he had been involved in torture and other human rights abuses while serving as DFS director from 1977 to 1982. Nazar Haro became an embarrassment for the government when it was disclosed that he had been indicted in San Diego in 1981 and 1982 in connection with a massive car-theft ring that stole luxury vehicles in the United States and supplied them to DFS officers and other Mexican officials. Also indicted in the same case were Prado, Perez Carmona and at least two other former DFS agents currently serving in top posts in the Intelligence Directorate. One of the two, Esteban Guzman, was identified in Mexican press reports Saturday as one of the detainees in the Buendia affair. But a spokesman for the attorney general's office said Guzman was neither in custody nor wanted in the case. The newspaper La Jornada reported today that fewer than 100 of the Intelligence Directorate's 500 employees remain on the job, the rest having resigned, requested leave or deserted following the arrests of Prado and Perez Carmona. It said the remaining agents now are commanded by Guzman, a subdirector of the Intelligence Directorate. Both Nazar Haro and Guzman have been accused in recent U.S. court testimony of having protected drug-trafficking operations in Mexico in the late 1970s and early 1980s. Nazar Haro, who denies all the allegations against him, has dropped out of sight. Zorrilla, who succeeded Nazar Haro as DFS director in 1982, resigned the post abruptly in March 1985 amid allegations that he had links with drug traffickers and was involved in a coverup of the February 1985 murder of U.S. Drug Enforcement Administration agent Enrique Camarena. The ruling Institutional Revolutionary Party (PRI) made Zorrilla one of its congressional candidates when he quit the DFS, but withdrew his candidacy three months later. Political analysts are watching the Zorrilla case closely for any repercussions against his superiors, notably former president Miguel de la Madrid and Manuel Bartlett, the interior secretary in the de la Madrid administration and currently secretary of education. Zorrilla in 1985 was considered a close protege of Bartlett, who competed with Salinas for the PRI's presidential nomination in 1987. In denying the charges against him, Zorrilla told a pretrial hearing last week, "I was not an autonomous official; I was a member of a government." He later told reporters pointedly that he had "served the system loyally for many years."