The official status is: unsolved, and it probably always will be.

Aside from many, many books that produce an astonishing amount of suspects, NIOD (the Dutch research institute for war crimes, genocide and the holocaust) undertook a massive investigation in 1986, and reopened the case in 2003 when two new credible suspects had emerged.

The report can be downloaded through [the website of the Anne Frank association] (http://www.annefrank.org/en/Anne-Frank/Discovery-and-arrest/The-betrayal-has-never-been-solved/NIOD-investigation/)