The late Cornelius Gurlitt, the collector of a billion dollars’ worth of art work, which he kept hidden in his apartment for decades. Photo: “60 Minutes”/YouTube/Screenshot.

The World Jewish Congress (WJC) expressed dismay over a German art exhibit, slated to open at the end of 2016, featuring pieces potentially looted by Nazis during World War II, Germany’s Deutsche Welle‎ reported on Saturday.

German Culture Minister Monika Gruetters said she hopes to open an exhibit showcasing art accumulated by the late collector, Cornelius Gurlitt — who had hidden a billion-dollar trove in his apartment for decades. The plan is for the exhibit to be shown at the Bundeskunsthalle museum in Bonn. The German magazine Der Spiegel reported that it could contain works stolen by Nazis from their original Jewish owners, and later accumulated by Gurlitt.

Ronald Lauder, president of World Jewish Congress, told Deutsche Welle‎ that he is disappointed with Germany’s lackluster efforts to return the looted art to heirs of its original owners. Referring to the task force established in 2013 to examine the pieces in Gurlitt’s collection, Lauder said that though he had been optimistic about it at the time, in the two years that have passed since then, only four pieces were determined to have been looted from Jewish families by the Nazis — and were handed over to relatives.

“Germany could have achieved more in that time, and still has a mandate to accomplish much more,” he said.

Gruetters’ office responded that a 2014 agreement allows for works from Gurlitt’s collection that had been looted, or whose background has not been identified, to be “exhibited with the aim of full transparency.” The culture minister told Der Spiegel that while exhibit organizers had to show “respect for the victims” whose art was stolen, she hopes a public showing of the works will help in the discovery of additional details about their true origin.

The Gurlitt task force is expected to end its work at the end of this year, according to Deutsche Welle. Gruetters said she wants the government-backed German Lost Art Foundation to be in charge of any further research efforts that are needed.