An initial police review of 3,300 such unsolved violent crimes between 1990 and 2011 had found that 746 of them, resulting in 849 deaths, will need a second look to see whether they were racial hate crimes, said the interior ministry.
The outcome is expected in the second quarter of next year, said a ministry spokesman, who cautioned that the review does not mean "that they are indeed crimes motivated by right-wing extremism."
Current statistics say about 60 people were killed in right-wing crimes since Germany's reunification in 1990.
Critics have long charged that official statistics underestimate the incidence of racist, xenophobic and other right-wing violent attacks, and complained that states use different standards in collating the figures.
The Green Party's parliamentary leader Katrin Göring-Eckardt said on Wednesday that authorities had "completely misjudged" the true extent of right-wing violent crime.
The chairwoman of the anti-xenophobia Amadeu Antonio Foundation, Anetta Kahane, accused the government of playing down the issue and challenged it to "face the fact that right-wing extremist violence is a huge problem".
Germany was shocked by news in 2011 that a series of 10 murders of mostly Turkish immigrants was committed by a three-member neo-Nazi cell that authorities now consider a terrorist group.
Beate Zschäpe, the only surviving member of the self-styled National Socialist Underground (NSU), is now on trial in Munich over the killing spree, which also claimed the lives of an ethnic Greek man and a German police woman.
The review announced Wednesday was sparked by the NSU case, which also motivated a new legal push launched this week by Germany's 16 states to seek a ban of the far-right and openly racist National Democratic Party of Germany.