Argentine forensic experts have begun work to trace the source of unidentified DNA found at the home of a prosecutor who died mysteriously while investigating alleged misconduct by President Cristina Kirchner.

Fabiana Palmaghini, the judge in the case, filed court papers on Tuesday saying a sample "corresponding to a genetic profile different" from prosecutor Alberto Nisman had been found.

"It remains unknown who the genetic profile that differs from Nisman's corresponds to," the AFP news agency quoted her as saying. 

People who visited Nisman in the days before his death will be called to give DNA samples, the judge said.

The unidentified DNA was discovered by investigators searching Nisman's Buenos Aires apartment, after he was found dead on January 18.

Nisman, 51, was found with a gunshot wound to the head on the eve of a congressional hearing at which he was expected to accuse Kirchner of shielding Iranian officials from prosecution, over a 1994 bombing at a Buenos Aires Jewish centre that killed 85 people.

The death was initially labelled a suicide, but suspicion has fallen on Kirchner's government of orchestrating Nisman's murder.

Conspiracy theories

The case has also spawned other conspiracy theories involving rogue intelligence agents and a group of Iranians accused of links to the Buenos Aires bombing 21 years ago.

Messages from the government have been contradictory, leaving Argentines scratching their heads over the prosecutor's death.

Gustavo Lopez, an undersecretary in the presidency, was quoted by Reuters as saying on Monday that the mysterious death was part of "an attempted coup d'etat, that aims to get rid of the president."

Anibal Fernandez, the president's chief of staff, who is not related to the two-term head of state, told reporters on Tuesday that everything pointed to Nisman having taken his own life.

The president for her part has suggested Nisman was manipulated by disgruntled former intelligence agents who then killed him to smear her.

Nisman had accused Iran of ordering the bombing at the Argentine Jewish Mutual Association via Lebanon-based Shia movement Hezbollah.

Four days before he was found dead, Nisman filed a 300-page report accusing Kirchner and Foreign Minister Hector Timerman of trying to cover up high-ranking Iranian officials' involvement in the attack in exchange for oil.

Source: Agencies