Argentine investigators say they have found a second person's DNA in the apartment where prosecutor Alberto Nisman was found dead and have called in a witness to check for a match.

Nisman's mysterious death came as he was presenting allegations that President Cristina Fernandez had conspired to protect Iranian officials implicated in the bombing of a Jewish community center in which 85 people died.

The statement released by the office of Judge Fabiana Palmaghini says she is calling in a person who visited Nisman the day before his body was found. She does not name him, but Nisman aide Diego Lagomarsino has acknowledged visiting Nisman on Jan. 17.

Investigators say they don't yet know if Nisman committed suicide or was killed.