Argentine forensic experts began work Tuesday to trace the source of unidentified DNA found at the home of a prosecutor who died mysteriously hours before a trial in which he was to accuse President Cristina Kirchner of a cover-up for Iran.

Investigators searching prosecutor Alberto Nisman's Buenos Aires apartment after he was found dead on January 18 uncovered DNA that differed from his but has not yet been identified, reports AFP.

"It remains unknown who the genetic profile that differs from Nisman's corresponds to," said Judge Fabiana Palmaghini.

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 center that killed 85 people.

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

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

Nisman had exposed how Iran ordered the bombing at the Argentine Jewish Mutual Association via its Lebanese-based Shi'ite proxy terror group Hezbollah.

Four days before he was found dead, he 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.