The United States Postal Service on Thursday announced that it would begin restricting “the domestic shipping of mailable motorized balance boards, or hover boards, that contain lithium batteries.”

The power source of the popular hands-free skateboards has become an extreme safety hazard, having been the cause of at least one massive explosion and several other fires.

The limitations, effective immediately, mean that USPS will only ship the popular hands-free skateboards on the ground through Standard Post, which excludes first-class shipping and, according to the post office’s website, “is commonly used for gifts and merchandise.”

In its statement, the USPS said that it had reached the decision after working closely with major airlines and retailers. On December 10, the three biggest U.S. airlinesannounced a hoverboard ban.

Retailers such as Amazon, as well as British retailers Tesco, Argos, and John Lewis have also reacted to the potentially dangerous scooters, either by urging customers to dispose of their hoverboards or to halt sales altogether.