Star's fashion line makes it big on auction site

Clothing retailer H&M on Thursday debuted the Designed by Madonna line, and many of the items have already landed on eBay.

“We are watching where the items appear,” H&M spokeswoman Jenni Tapper-Hoël tells PEOPLE.

“We prefer people to buy our garments in stores,” but the chain doesn’t mind the online auctions “provided it is a few pieces that are being sold by people and not a big party behind it.”

H&M has branches in 18 states and Washington, D.C., and some shoppers had lined up at dawn to be first through the doors. Hot items include the Madonna trenchcoat, sunglasses, kimono silk dress and capri pants, all of which are already for sale online – with some trenchcoats offered at double the retail price.

“We also saw this happen when we sold ranges for Karl Lagerfeld, Stella McCartney, as well as Viktor & Rolf,” says Tapper-Hoël. “We can’t do anything about it.”

H&M previously collaborated with Madonna last year for her Confessions Tour, on which all tour members – including the band, dancers and crew – wore H&M designs. As part of the cross-promotion, the store sold a specially designed Madonna tracksuit and she her singers appeared in ads for the company.