A Nazi-looted painting that was hidden for decades smashed expectations at a rare sale in London on Wednesday, AFP reported, as investigators work painstakingly to identify the origins of hundreds of other works from the same haul.
Max Liebermann's "Two Riders on a Beach" was found among more than 1,200 works of art in the Munich apartment of German recluse Cornelius Gurlitt when police raided it in 2012, capturing global attention.
The 1901 oil painting went under the hammer at Sotheby's for £1.865 million ($2.92 million, 2.61 million euros), more than three times the pre-sale upper estimate of £550,000, according to AFP.
It is the first from the Gurlitt collection to be auctioned off while the origins of many of the works remain unknown.
"The challenge is to go through the provenance of every single picture in this collection," Sotheby's director Bernhard Brandstaetter said.
"It is a lengthy process to establish where a picture comes from, when it was bought and so on," he added, describing the collection as "probably the most significant find in the last 30 years".
Richard Aronowitz, European head of restitution for Sotheby's, described the Liebermann painting as a "scene of great tranquility and joy in nature", adding, "This counterbalances the great sadness and trauma of the work's history."
Wednesday's auction also included a Gustav Klimt portrait lost to Jewish owners during the Nazi regime and had come on sale after the resolution of a dispute between descendants of the artist and the subject.
The painting went for £24,789,000, exceeding the pre-sale estimate of £18 million.
Helena Newman, Sotheby's co-head of impressionist and modern Art, described it as "one of his finest portraits to appear at auction in over 20 years."
David Toren, one of several heirs of the Liebermann painting, was just 13 when he saw the picture being taken by the Nazis from the estate of his great-uncle David Friedmann in 1938, the day after the Kristallnacht pogrom.
Now, aged 90 and blind, Toren said he is unable to appreciate the painting, returned after a legal battle as the German government still seeks to establish the provenance of other works in the hoard.
Paintings by Picasso, Manet and Chagall were among the huge trove discovered when German police raided Gurlitt's unassuming apartment in Munich.
The Liebermann painting was sold by the Nazis, ending up in the hands of Hildebrand Gurlitt, an art dealer tasked by Hitler to plunder works from museums and Jewish collectors.
The works were inherited by his son Cornelius, who himself died last year.
"Since then it has disappeared from public view," said Brandstaetter. "What's so surprising is that it was hidden away for so long.
"When it arrived here it was very dirty. You could see it had not been cared for. Many of the things Cornelius Gurlitt had in his house were just stuck somewhere, behind cupboards or under beds."
It is one of only two paintings from the Gurlitt stash to be returned to their owners.
The Kunstmuseum Bern is working with German authorities to find other rightful owners -- but faces a laborious task.
Germany has been sharply criticized for its "scandalous" handling of the art findings, as news of the looted trove was only made public through a news report. Following the criticism, Germany created a site to facilitate the return of the art by increasing access to images of the pieces.
A Swiss museum that accepted Gurlitt's bequest of his collection and a cousin who challenged his will both promised to ensure any Nazi-looted pieces are returned to their Jewish owners' heirs.
AFP contributed to this report.