Argentine forensic experts have discovered DNA from an unidentified person in the apartment of special prosecutor Alberto Nisman who died Jan. 18 under what have been regarded as highly mysterious circumstances.

Nisman, who was just about to testify against Argentine President Cristina Fernandez de Kirchner, was found shot in the head in his apartment. The prosecutor had openly accused the president of covering up an Iranian involvement in the 1994 attack on a Buenos Aires Jewish center that ended in the deaths of 85 people. Fernandez and the country of Iran have both rejected Nisman’s allegations.

Nearly a month after Nisman was found dead, investigators are still trying to figure out if the man committed suicide, was forced to commit suicide, or was indeed murdered. The investigator in the case, Judge Fabiana Palmaghini, has ordered tests to identify the genetic material found in Nisman’s apartment. Any persons who could have visited Nisman on the day of his death will be asked to come forward to provide a DNA sample.

Diego Lagomarsino, a long-time acquaintance of Nisman, has said that he was in the apartment on Jan. 17. Lagomarsino lent Nisman a gun which was later found next to his body. As reported by BBC, Lagomarsino said the prosecutor asked him for the gun because he "feared for the safety of his daughters."

President Fernandez has accused Lagomarsino of opposing the current Argentine government.

She believes that Nisman was manipulated by a rogue intelligence agent that fed the prosecutor bad information, and has gone so far as to table a bill designed to disband Argentina's intelligence service.

The opposition party has accused the government of ordering Nisman's death in order to keep him from testifying.

Nisman published a 300-page report on the attack on the Amia Jewish center just days before his scheduled hearing in congress.