An electric unicycle that was plugged into a wall for charging may have caused a substantial fire a Manhattan residential building on Wednesday afternoon.

The FDNY says that they received calls about the fire at 99 University Place just after 4:30 p.m. The inferno climbed to two alarms, and 25 units and 100 firefighters responded to the scene.

#FDNY members continue to operate on scene of 2-alarm fire, 99 University Place in Manhattan. pic.twitter.com/1SRQVFfAlt
— FDNY (@FDNY) May 8, 2019

Fire @ 99 University Place @Gothamist pic.twitter.com/Qyi7nFaSn2
— Personal expression (@pincusy_pincus) May 8, 2019

The blaze was under control by 5:33 p.m. FDNY Fire Marshals said the source of the fire was an "accidental, electrical fire caused by an electrical unicycle that was plugged into an outlet in the building."

Two firefighters suffered minor injuries.

Fires—and, in some cases, explosions—have occurred while electric unicycles and hoverboards are charging, prompting recalls of some products.

CNET explained what leads to fires, "The science behind hoverboard fires is actually pretty simple, and fairly well understood. Much like your laptop, tablet or phone, these hoverboards use lithium ion battery packs for their power, and it just so happens that the liquid swimming around inside most lithium ion batteries is highly flammable. If the battery short-circuits -- say, by puncturing the incredibly thin sheet of plastic separating the positive and negative sides of the battery -- the liquid electrolyte can heat up so quickly that the battery explodes."