Finding the treasure hoard was just the start of the hunt.

Phones in the cramped London offices of the Art Loss Register have been ringing off the hook since German prosecutors announced what the register's chairman, Julian Radcliffe, calls "the biggest cache of illegally stored art since the end of the war."

"People who are registered with us have been ringing to say, `You're on the case, aren't you?"' Radcliffe said Wednesday.

The flurry of activity follows the discovery in Germany of more than 1,400 artworks -- some by modern masters such as Marc Chagall, Henri Matisse and Pablo Picasso -- stacked in the Munich apartment of an elderly man. For families whose treasures were stolen by Germany's Nazi regime, the discovery has raised hopes -- but also stirred frustration.

Citing an ongoing tax probe into the apartment's resident, German authorities have not revealed many details about the vast majority of the paintings, drawings, engravings, woodcuts and prints they have found. At a news conference Tuesday, officials described only a fraction of the spectacular find, including -- tantalizingly -- previously unknown paintings by Matisse, Chagall and German artist Otto Dix.

That has sparked a clamor for information from art hunters, museums and the lawyers of those seeking to recover looted art.

On Wednesday, a lawyer for the family of the late Parisian art dealer Paul Rosenberg said he was "in the process of submitting a claim" for one of the most spectacular works, a Matisse painting of a seated woman.

"I fully expect when they get my claim letter they will invite me to Munich" to negotiate its return, Chris Marinello, director of the London-based Art Recovery International, told The Associated Press.

Rosenberg lost hundreds of artworks when the Nazis invaded France in 1940. His relatives, including granddaughter Anne Sinclair -- the French journalist and ex-wife of former International Monetary Fund chief Dominique Strauss Kahn -- have sought for decades to retrieve them.

The Munich trove was found in early 2012 at the home of a man whom German officials didn't name but who has been identified in media reports as 80-year-old Cornelius Gurlitt. His father, Hildebrand Gurlitt, was an art dealer who acted for the Nazis in the 1930s to sell art considered "degenerate" by the regime -- including Impressionist and modern masterpieces -- outside of Germany in return for cash.

Some of the works were seized from museums, while others were stolen or bought for a pittance from Jewish collectors who were forced to sell.

Gerhard Finckh, director of the Von der Heydt-Museum in Wuppertal, western Germany, called for an inventory of the Gurlitt trove to be published online quickly so museums can find out whether their stolen works are among them.

"If our works are among the discovered art, we will do everything to get them back," said Finckh, whose museum lost pieces by Dix, Paul Klee, Vassily Kandinsky and many others.

Jewish groups also have called for the works to be made public immediately.

Spokesman Steffen Seibert said Wednesday that Chancellor Angela Merkel's government favored releasing information about works that "may have been confiscated from people persecuted by the Nazis." But he gave no details or timeframe for that to happen.

That leaves people seeking the return of artworks with no quick path to restitution.

Imke Gielen, a Berlin lawyer specializing in restitution claims, said prospective claimants should approach the Bavarian prosecutors with queries about specific works. She said it was vital to prove ownership of the artwork until Jan. 30, 1933, the day the Nazis seized power. Any art lost after that is presumed to have been sold under pressure or seized, boosting the chances of restitution.

Others will turn to the Art Loss Register, which maintains a database of several hundred thousand works of stolen or missing art.

The organization's team of art sleuths, historians and legal experts was busy Wednesday trying to match works on its database with the items found in Germany. Radcliffe says it has already found one match -- not the Matisse -- but won't say what artwork it is.

Although there has been criticism of the Germans' delay in announcing the find, art law expert Coco Soodek was sympathetic. She said the trove is so large that it takes time to catalog the works -- and "it might take a decade" to reunite them with their owners. German officials say they have done preliminary work on only 500 pieces so far.

"It's like a giant game of `Concentration,"' said Soodek, head of the art law team at Bryan Cave LLP. "They will designate the ones that we know to exist and match those up with documentation of stolen art. Those are the easy ones. You match up the ones you can get to first, and then you start a big detective search."

She said families who think their artworks may have been stolen by the Nazis "should do a little treasure hunt for records -- oral histories or anecdotes or memories of art that might have been in the house."

For the moment, many mysteries remain.

The reclusive Gurlitt sold at least one painting, Max Beckmann's "The Lion Tamer," through a Cologne auction house two years ago. Experts want to know whether he sold others, and where they are now.

Where, for that matter, is Gurlitt? Prosecutors said Tuesday they are not currently in contact with him, although Radcliffe thinks they will seek to strike a deal with him to hand over his artworks in lieu of a huge tax bill.

And prospective owners can be reassured on one count. A German customs investigator says the works were "professionally stored and in a very good condition."

Radcliffe said while works on paper could be fragile, oil paintings on canvas or board should be largely undamaged after decades in storage.

"Oil paintings are fairly robust," he said. "They don't really deteriorate."