WASHINGTON — The fallout over the potential for Samsung Galaxy Note 7 smartphones to catch fire is intensifying.

On Friday, the United States Consumer Product Safety Commission urged owners of the smartphone to power down their Galaxy Note 7 devices and stop using them altogether.

“C.P.S.C. and Samsung are working cooperatively to formally announce an official recall of the devices as soon as possible,” the agency said in a statement. “C.P.S.C. is working quickly to determine whether a replacement Galaxy Note 7 is an acceptable remedy for Samsung or their phone carriers to provide to consumers.”

The C.P.S.C. is the main consumer product safety agency in the United States, with broad oversight over toys, tractors, appliances and electronics. This year, the C.P.S.C. recalled hoverboards that contained lithium-ion batteries; those batteries exploded or caught fire in dozens of cases.