Data records combed by investigators included "photo files relating to the Schumacher family's private life", the prosecutors in the western city of Wuppertal said in a statement.
German authorities announced in June they had arrested a father and son on suspicion of trying to blackmail the Schumacher family.
The suspects contacted family representatives claiming to have access to files which the Schumachers "would not want to have published", prosecutors said.
"To stop the files being published online, the perpetrators demanded a payment in the millions," they said.
The suspects allegedly transferred "individual files" to the family in a bid to show they were not bluffing.
Michael Schumacher, a seven-time Formula One world champion, has not been seen in public since he suffered a serious brain injury in a 2013 skiing accident in the French Alps.
The two suspects, who were on probation in another case, were arrested by police on June 19 in a supermarket car park in Gross-Gerau, south of Frankfurt.
Prosecutors on Wednesday said "intensive investigations" were being carried out into the case but no further details could be given "for reasons of investigative tactics".
Schumacher's family in May won a legal action against a German tabloid magazine which printed a fake AI interview with the 55-year-old German former race driver.
Magazine Die Aktuelle had in April 2023 claimed it had an interview with the motorsport legend but the article in fact contained quotes which had been computer-generated.
German tabloid Bild reported that Schumacher's family was awarded 200,000 euros ($220,000) in compensation for the claim.
