If you bring a hoverboard on the New York City subway, you might just get kicked out.

The NYC Metropolitan Transit Authority (MTA) last month banned hoverboards on subways and busses, and has now put up posters in underground subway stations and at Long Island Railroad entrances warning straphangers not to use — or even carry — hoverboards, according to Mashable.

"Hoverboards not allowed," the signs read. "You cannot bring one into the subway, onto a bus nor into rail cars or stations. No carrying, no standing, no riding — no exceptions."

The MTA goes on to say that "Hoverboards may be the latest fad, but they are not safe because they have the potential to catch fire."

Where can you ride hoverboards in the Big Apple? Private property, it seems. The city banned them on city streets late last year; riding them could result in a $200 fine.

This comes less than a week after the U.S. Consumer Product Safety Commission issued an official warning to manufacturers, importers, and retailers of self-balancing scooters: Get your devices certified, or risk civil and criminal penalties. In a letter, the CPSC urged hoverboard makers and sellers to ensure their devices comply with new safety standards, and voluntarily take them off the market until they can be deemed safe by an independent testing firm.

The commission said it has received reports from consumers in 24 states of 52 self-balancing scooter fires between Dec. 1, 2015 and Feb. 17, 2016. Together, these incidents resulted in more than $2 million in property damage, "including the destruction of two homes and an automobile," the agency said.

This article originally appeared on PCMag.com.