Mexico Investigator Quits, Says PRI Thwarting Probe : Assassination: Ruiz Massieu accuses party officials of cover-up in brother’s slaying. They deny charge.

Mexico’s second-ranking law enforcement official resigned Wednesday from his job, from the ruling party and as chief investigator in the assassination of its secretary general, publicly accusing the party’s top officials--including his boss, the attorney general--of covering up a murder he blamed squarely on the party.

To shouts of “No! No! No one else can be trusted!” Deputy Atty. Gen. Mario Ruiz Massieu told hundreds of supporters, packed beyond capacity into an auditorium in the attorney general’s headquarters, that “the resistance and the obstacles the party has put in the way of the investigation” made it impossible to proceed further.

The prosecutor announced that his two-month investigation had amassed enough evidence to warrant the arrest of several officials for complicity or obstruction of justice in the gangland-style slaying of his brother, Francisco, who was the Institutional Revolutionary Party’s second-ranking official when he was gunned down outside a Mexico City hotel in September.

“Last Sept. 28, a bullet killed two Ruiz Massieus--one lost his life, and the other lost his faith and his hope that a PRI government could bring justice,” he declared.

Ruiz Massieu said a report he sent to President Carlos Salinas de Gortari on Wednesday morning contains sufficient proof of wrongdoing to strip away all immunity from the woman who succeeded his brother as PRI secretary general, Maria de los Angeles Moreno, an elected member of the Mexican Senate who he said should be arrested “for various crimes.”

The prosecutor said the evidence also implicates party president Ignacio Pichardo in “shameful” acts, including obstruction of justice and conspiracy, a charge he also leveled against his immediate superior, Atty. Gen. Humberto Benitez Trevino.

Pichardo demanded, on behalf of the PRI, details of Ruiz Massieu’s evidence--which the prosecutor stopped short of releasing Wednesday. Rather, Ruiz Massieu said, he sent the documents to authorities--particularly Salinas and the ruling party’s president-elect, Ernesto Zedillo.

At a hastily arranged news conference Wednesday night, Pichardo “categorically” denied the accusation, which he called “defamatory and slanderous.”

Seated beside Moreno, he accused Ruiz Massieu of investigating the case “without strictly adhering to the law,” adding that the party leadership is consulting with its attorneys to determine what action, if any, to take against “the former deputy attorney general.”

Moreno remained stony-faced and silent throughout the news conference. But on Tuesday, in testimony before the Senate, Moreno insisted she had demonstrated a clear willingness to aid the investigation into her predecessor’s slaying.

“For this reason,” she said, “I cannot accept the false and deceitful accusations that have been made against my party, against its various members . . . and me.”

Ruiz Massieu challenged Zedillo to follow up the investigation and formally charge the top hierarchy of his own party when he assumes office a week from today. “The president-elect must act,” Ruiz Massieu declared. “Society insists on it, the Ruiz Massieu family demands it and justice obliges it.”

Zedillo, who was in Washington to meet President Clinton on Wednesday, reacted calmly to the allegations, which touched off a political firestorm in Mexico City. He told a news conference in Washington that he had yet to see the evidence and would reserve comment, but added that he was committed to reforming Mexico’s criminal justice system and to solving the slaying.

It was clear that Ruiz Massieu had presented the 41-year-old Yale-educated Zedillo, an economist who was elected with the smallest majority in ruling-party history in August, with an acid test of his vow to continue Salinas’ democratic reforms. Salinas appointed Ruiz Massieu to investigate his brother’s slaying as part of those reforms.

“It is unfortunate that some politicians do not understand that the country has changed, and that old corrupt and even illegal practices must be put to one side,” Ruiz Massieu said. “It is unfortunate that in the case of Francisco Ruiz Massieu, it has been the PRI - istas themselves who eliminated him. It is unfortunate that those same PRI-istas continue in power.”

In thanking Salinas for his support and commitment throughout the investigation, the prosecutor underscored what many Mexican political analysts say forms the core of Zedillo’s challenge in the years ahead: reforming a party that, after governing continuously since 1929, has become more powerful than the president.

“The PRI political class had more power than a president . . . more power than the justice that a president demanded,” Ruiz Massieu said, referring to Salinas, who Wednesday afternoon confirmed that he had received the report containing the prosecutor’s evidence and thanked Ruiz Massieu for his work and his courage.

The justice that Ruiz Massieu did manage to exact before his resignation includes the arrest and detention of 14 suspects in his brother’s case, among them low-ranking PRI officials, legislative aides and the hired gunman who was tackled at the murder scene.

A more senior member, former PRI legislator Manuel Munoz Rocha, has been named as a co-conspirator and mastermind of the assassination, but he remains at large despite an international search.

Throughout the series of arrests, Ruiz Massieu released the detailed testimony of each suspect, drawing praise from a public unaccustomed to official openness and intense political fire from a ruling party unaccustomed to public scrutiny.

Times Washington Bureau Chief Jack Nelson contributed to this report.