March 27 (Bloomberg) -- Chile's former dictator, Augusto Pinochet, is under investigation again, three and a half months after his death at the age of 91.

The question is whether Pinochet ordered government agents to kill ex-President Eduardo Frei Montalva with mustard gas in 1982.

Scientists hired by a Chilean investigating judge found traces of the poison in Frei Montalva's exhumed remains. The court probe also discovered that minutes after the former president died, doctors without identification tags locked his room, drained fluids from his body and removed most of his organs, Frei family lawyer Alvaro Varela said.

``These kinds of things are only explainable by the climate of horror that Chile lived through,'' President Michelle Bachelet said in January at a memorial service in honor of Frei Montalva, president from 1964 to 1970. ``After 17 years of democracy, we still don't know the truth about the horrible deaths and the disappearances.''

For the thousands of Chilean families who lost loved ones during Pinochet's 1973-1990 military dictatorship, probes into his alleged violations of human rights and financial crimes may help provide a sense of justice. The investigation into the death of Frei Montalva will show that Pinochet was just as committed to holding power as he was to eradicating Marxism, Varela said.

``There's enough evidence to affirm that the death of President Frei Montalva was a homicide,'' Varela, 56, said in an interview in Santiago. ``We've determined with certainty that he was a target of the dictatorship.''

President's Loss

Pinochet, who died of natural causes in December, headed a regime that killed more than 3,000 opponents, according to a government panel established after Chile's return to democracy in 1990. Bachelet, 55, a Socialist who in 1975 was imprisoned and beaten by military officers, denied Pinochet a state funeral. Her father, a general opposed to Pinochet, died in prison in 1974.

``This case has nothing to do with the Pinochet family,'' said retired General Guillermo Garin, a spokesman for Pinochet's widow and children. The news media are stirring up controversy over Frei Montalva's death, which long was accepted as a natural one, he said. Pablo Rodriguez Grez, an attorney who represented Pinochet in several criminal cases, didn't return phone calls seeking comment.

Frei Montalva's son Eduardo Frei Ruiz-Tagle, the president of Chile's Senate, filed a petition in January asking Judge Alejandro Madrid to rule his father's death a homicide and to shift the official goal of the probe to solving the crime.

As an investigating judge, Madrid has the power to continue his probe indefinitely until he has evidence to bring charges and try anyone involved who is still alive, said Alfredo Ugarte, a lawyer at a foundation dedicated to preserving Frei Montalva's memory. The judge also could award damages to Frei Montalva's family or conclude the matter by issuing a report on his findings, he said.

Conflict Over Constitution

Pinochet's enmity for Frei Montalva developed during the run-up to a 1980 plebiscite on a new constitution that the military government wrote after seizing power from Socialist President Salvador Allende seven years earlier. Frei Montalva became a target of the regime because he resisted changing the 55-year-old constitution, Varela said.

Before the vote, Frei Montalva spoke at a rally in Santiago and called for a return to democracy, making him one of Pinochet's key adversaries, said his grandson Eugenio Ortega Frei.

Varela said Frei Montalva's murder offers proof that the aim of Pinochet's government wasn't just to fight the socialism promoted by Allende, who died in the 1973 coup that brought Pinochet to power.

Frei was against Allende, said Varela, who specializes in investigating human rights crimes. While the dictatorship said it was fighting Marxism, it really was fighting anyone who threatened its power, he said.

`Darkest Part'

``We've entered into the darkest part of the military government -- the production and use of chemical weapons to kill people,'' grandson Ortega Frei said. ``We want to know the truth about what happened.''

Public interest in Frei Montalva's death surged after state- run Television Nacional broadcast a two-part documentary on the case in August.

It includes interviews with witnesses who spoke on condition of anonymity and was the first time the media had pointed to evidence of homicide, said Mirna Schindler, 39, the lead journalist in the report.

Pandora's Box

``The story opened a Pandora's box,'' said Schindler, who spent nine months on the project. ``Chile started talking about something it hadn't talked about for 26 years.''

Some Chileans still defend Pinochet, crediting him with imposing policies that laid the groundwork for South America's highest per-capita gross domestic product. It was $5,870 in 2005, according to the World Bank.

Schindler said that after the broadcast, strangers called her ``shameless.'' A few months later, more than 60,000 mourners filed past the former dictator's casket at a military wake.

``We've been a democracy for almost as long as we were a dictatorship,'' said Gabriela Zuniga, 53, a director of an advocacy group that represents families of people who, like her husband, disappeared. ``It's just in the last few years that these investigations have advanced and we've started to determine who was responsible.''

To contact the reporter on this story: Matthew Walter in Santiago at mwalter4@bloomberg.net

Last Updated: March 27, 2007 00:22 EDT