German media report that authorities have mistakenly shredded dozens of binders containing files on far-right extremists.

News agency dapd reported that local lawmakers in the state of Berlin were informed of the incident Tuesday.

The news portal Spiegel Online reports that Berlin state's domestic intelligence service destroyed the files in June even though they were destined for official archives.

The website quotes Berlin's top security official, Frank Henkel, as saying none of the files likely related to far-right National Socialist Underground, which is suspected of killing 10 people between 2000 and 2007.

Blunders in the investigation of the NSU have prompted four senior German security officials to resign over the past year.

Prosecutors said Tuesday they plan to file charges soon against "several people" accused of involvement with the group.