An employee poses for a photograph with Banksy’s "Love is in the Air" (L), "Leopard and Barcode" and "Bomb Hugger" (R)
An employee poses for a photograph with Banksy's "Love is in the Air" (L), "Leopard and Barcode" and "Bomb Hugger" (R) at Bonhams auction house in London. (Reuters/Luke MacGregor)
A mural by famed street artist Banksy is up for sale at a Miami auction house after the work, and a chunk of the North London wall it was spray-painted on, vanished late last week.

Who owns the mural is unclear, and how it ended up in a Miami auction house shortly after going missing is still a mystery. Frederic Thut, owner of Fine Art Auctions Miami, which is selling the piece, said his firm has done "all necessary due diligence" to establish the ownership of the work.

"Unfortunately we're not able to provide any information by law and contract about the details of this consignment," he said.

The mural was painted on a building occupied by Poundland Stores, a British retailer that sells various items for only a pound. The work, titled "Banksy: Slave Labour," shows a young boy kneeling at a sewing machine with Union Jack bunting.

It appeared in 2012 during Queen Elizabeth II's Diamond Jubilee, celebrating her 60th year on the throne. The Poundland chain was a focal point of controversy in 2010 when it was alleged that it sold goods made by Indian children as young as seven.

"We lease the premises from a landlord and were as shocked and surprised as anyone at the removal of the Banksy artwork," Kate Gibson, a spokeswoman for Poundland, wrote in an email. "We understand the upset this has caused and in no way do we condone the removal of the artwork without proper consultation with the community."

Gibson didn't say whether Poundland officials have spoken with the landlord and she couldn't provide any details on the property owner.

Meanwhile, the work remains listed on the auction house's website, where it has received three bids and is valued between $500,000 and $700,000. Described as a "unique street work" of "stencil and spray paint on render with additional jubilee bunting," it is due to be auctioned on Saturday.

The elusive artist's trademark spray-paint stencils offering ironic social commentary are never verified, though they are hotly sought after by collectors.

One West Bank mural shows a young girl frisking a soldier who looks to be leaning up against a wall with his arms outstretched. Another is of a man with a bandana wrapped around his face looking as though he's throwing a grenade, though a bouquet of flowers takes the place of the explosive.

"Banksy goes to a property anywhere around the world and he puts something without asking you on your wall," said Stephan Keszler, a New York City gallery owner who specializes in Banksy's work. "People call it vandalism, therefore he's not authenticating the works because this would admit that he made a crime."

Keszler brought more than a half dozen Banksy murals - massive concrete slabs weighing more than 2,000 pounds (907 kg) -- to a Miami art fair in December. Two were works he salvaged on behalf of building owners in the West Bank and later bought. The others were owned by collectors whom Keszler was advising on sales.

A group called Pest Control oversees authentication of the artist's works on paper, but the group is almost as elusive as Banksy himself. Keszler said Holly Cushing, a producer of the 2010 documentary about the artist, "Exit Through The Gift Shop," runs the group.

"Did you read one word from Pest Control the work is not a Banksy?" he asked. "The works are not fake, otherwise they would say they're fake."

Pest Control did not respond to a number of emails and calls seeking comment. Keszler argued that discussion of the issue of who owns the works, their authenticity and whether they should be moved will someday end.

"If a property owner wants to auction this at the auction house, he can do this with his property," Keszler said. "I believe that one day this discussion ... will be over, and then the people who were brave enough to buy those today, yesterday and tomorrow will have made a very good investment."