MINNEAPOLIS - Usually, when you hear about a "theft ring" getting busted you think jewelry, high-priced electronics, or just boatloads of cash. However, in the last two years, Lego bricks have become a lucrative lift for thieves.

Not just because they are valuable, but also, they are very difficult to track.

Dan Siskind, owner of Minneapolis-based Brickmania, has heard of the dark side of Lego.

“There's no serial number on a Lego set,” said Siskind. “You can't trace it back to a location.”

Brickmania buys large quantities of authentic Lego parts and repackages them into custom military kits, which Siskind designs.

“The Tiger Tank, which is actually one of our best sellers, is $400,” said Siskind.

Lego pieces and kits began rising in value in the early 2000s after the Danish company began partnering with blockbuster brands like Star Wars and amping up products marketed to adult Lego collectors. Limited edition, unopened sets can fetch thousands of dollars on the secondary market. Single pieces can cost up to $100.

And where there is value there is theft.

As first compiled by Vice, last summer an alleged crime ring was busted stealing $15,000 worth of toys, mostly Legos from San Diego County Toys R Us stores.

Two years ago, police say they uncovered more than $200,000 in stolen Lego sets in Arizona.

The same year, a New York woman was charged with lifting 800 sets of Lego worth nearly $60,000 and trying to sell them in eBay.

A few months ago, a 43 year-old in Oregon was allegedly caught on camera stealing a $450 R2D2 Lego replica.

Lego is often sold on the secondary market through eBay or bricklink.com.

Siskind says he mainly buys pieces only from reputable sellers he's worked with for years.

“There's absolutely no way [to know if it’s stolen], and if you are buying stuff on the aftermarket like eBay, you really don't know who you are buying from. The only way you are going to know is by checking reputation and even that it's not 100 percent certain,” said Siskind.

He says Lego lifters at any level paint a bad light on the whole industry.