BUENOS AIRES (AFP) - Unidentified DNA has been found at the home of an Argentine prosecutor who died mysteriously while investigating alleged misconduct by President Cristina Kirchner, a judge said Tuesday.

Investigators discovered the DNA on a coffee cup at prosecutor Alberto Nisman's Buenos Aires apartment, where he was found dead on Jan 18.

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

Judicial sources also said a second test for gunpowder residue on Nisman's right hand had come back negative.

That supports the results of a first test performed after Nisman's death that also found no trace of gunpowder on the hand that was clutching the .22-caliber revolver that killed him.

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

The President 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 the Lebanon-based Shiite movement 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.