Minister Priyank Kharge said the inquiry would examine the entire sequence of events, including who organised the alleged operation, its purpose, how the material changed hands and why it was uploaded and publicised years later.
He said Siddaramaiah had expressed confidence in the investigation and maintained that those behind any criminal conspiracy would be identified.
Kharge called for a transparent, impartial and swift inquiry, saying police were proceeding without interference or political pressure.
Responding to questions about the alleged involvement of Congress members, he said people whose names had emerged had been summoned and questioned. Their statements and questioning had been documented, he added, with details to be disclosed at an appropriate stage.
Kharge also said some individuals had reportedly become untraceable after notices were issued. Efforts were continuing to locate and question them, he said, without identifying those concerned.
With PTI inputs