A big I-Team investigation exposed an illegal, back-alley auto ring taking customers for a ride. Now, the State of Wisconsin is taking action.

This illegal lot was so well hidden, state investigators had no idea it existed until the I-Team led them to it.

We first met "Mike," the name he gave us, about a month ago at the corner of 38th and Mitchell Streets.

Mike agreed to meet our undercover producers there to look at some of the dozen or so cars he had for sale on Craigslist.

Turns out "Mike" was operating an illegal, unlicensed car lot hidden just a few blocks away.

"It makes me angry, because I can't do nothing," complained Anthony Bivins of Milwaukee. Bivins bought a 1992 Ford Taurus from Mike last month. It died less than two weeks later.

"Either I'm going to have to keep putting more money in it to help my daughter get the car running, or we're just going to have to accept the loss and junk the car."

The I-Team found other cars at Mike's lot with engine blocks missing bolts and leaking transmission fluid.

"I mean it's obvious he's not inspecting any of these vehicles," said Wisconsin Department of Transportation Inspector Scott Selbach.

We caught up with him again about a week later and asked him where he got all those cars he was trying to sell.

"I mean, it's not even your business," Mike replied. "It's not even your business, so I don't have to explain you nothing."

But Mike will have explain things to the DOT.

The State investigators swooped in earlier this month and shut the place down after we led them to the hidden lot.

"This is very concealed," said DOT Inspector Jim Bartnik. "That's why we didn't know anything about it until you guys."

Their job now: checking vehicle identification numbers to figure out where all these cars came from and how they got here.

Since the dealership is unlicensed, every car investigators find for sale could be a $450 fine. The DOT is writing up citations right now.