US Customs and Border Protection said this week that the agency seized 16,000 counterfeit hoverboards during a bust in Chicago. According to Customs, it's a record seizure of the fake boards.

As safety concerns have mounted over knockoff, low-quality boards, Customs has appeared to take a keener interest in stopping shipments from entering the US. Earlier this month, the agency said it had stopped a shipment of 300 counterfeit boards at the Port of Miami. Before that, it was 445 hoverboards at the Port of Norfolk, Virginia.

This week's case bears some similarities to the crackdowns before it. Customs said in a statement that the boards contained "unauthorized" batteries with fake trademark logos. (Batteries have previously been found marked with counterfeit LG and Samsung logos.)

The agency estimated that the hoverboards were worth more than $6 million on the market, but added that the whole stock is still being sifted through, and that the number could increase.