Authorities said Pirhya Sarusi and Lily Pereg, both Israeli citizens, visited Sarusi's son Gil Pereg before their disappearance and were buried in his possession in Mendoza on Saturday.
Gil Pereg, who lives in Argentina, is accused of murder, according to a statement by the Argentine Prosecutor General's Office.
One of the bodies had three gunshot wounds, and the other also had markers indicating a fight.
"There's nothing here, nothing illegal here," he told Todo Noticias.
Pereg said he hopes his mother and aunt would do it alive, but the police "coming here to disturb me" would not help in the search. He declined to let Todo Noticias into his house.
Lily Pereg was a professor at the Australian University of New England, whose main campus is in Armidale, New South Wales. Her website describes her as a microbiologist specializing in plant and soil microbiology.
The University said that Pereg became a lecturer there in 2001 and was recently appointed full professor.
"She has been recognized as a leading scientist in the field of soil microbial ecology and plant microbial interactions, both nationally and internationally," the school said in a statement.
"Our sincere condolences go out to the family, friends, colleagues and students of the sisters."
In an interview with CNN, Moshe Pereg, brother of the two sisters, before the bodies were found No information was provided in Gil Pereg's house. Moshe said Gil told him that Pirhya and Lily had left his home on the night of January 21st and gone to the bus station.