CHICAGO — All the burglars use the same audacious tactics: A vehicle crashes through a storefront in the wee hours and up to six people in dark clothing and ski masks pour out, grabbing whatever they can with the speed of a NASCAR pit crew.

Then the thieves dash out over the broken glass to a waiting getaway car.

Since September, at least a dozen “crash-and-grab” burglaries have been reported at retail businesses in Chicago and the surrounding suburbs. Some targeted high-end businesses, including a Neiman Marcus store on the famed Magnificent Mile. Others struck less affluent locations such as a pawn shop on the South Side and clothing stores on the far West Side.

The thefts have made shop owners nervous, and police are still pursuing their first arrest.

It’s not clear whether the same people are behind the heists, but the methods appear almost identical. In each case, the thieves use cars and trucks as battering rams to smash through glassy storefronts and, in at least one case, a brick wall. Police say they suspect the early incidents may have inspired others to copy the idea.

“What these crews do is basically assault the building,” said Eugene Roy, commander of a detective division for the Chicago Police Department. “These operations are very well planned.”

In less than two minutes, the thieves have made off with expensive jeans and other clothing, jewelry, tools, purses and anything else they can pull out of display cases or off the sales floor. Then they run away, leaving behind the debris-covered vehicles, which often turn out to be stolen.

The burglaries are not entirely new. Video of cars crashing through the front windows of convenience stores and other businesses can easily be found online. In the early 1990s, in New York, authorities indicted members of a highly organized group that crashed into fur salons, jewelry stores and art galleries, making off with paintings, mink coats and other loot.

Roy said police started seeing the tactics in Chicago about a year ago, a result, he suspects, of thieves recognizing that stores have gotten better at foiling the traditional burglar who cases a building and picks a lock. He said no arrests have been made in any of the crash-and-grabs since September.