The U.S. Consumer Product Safety Commission is urging consumers who have Samsung Galaxy Note7 smartphones to "power them down and stop charging or using" them.
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The warning, issued in a news release today, came amid recent news that lithium-ion batteries in certain Note7 devices had resulted in fires.
"When these batteries overheat and burst, the results can be dangerous," the CPSC said in its statement. "These incidents have occurred while charging and during normal use, which has led us to call for consumers to power down their Note7s."
The agency said it is working with Samsung to formally announce a recall of the devices.
"CPSC is working quickly to determine whether a replacement Galaxy Note7 is an acceptable remedy for Samsung or their phone carriers to provide to consumers," the agency said.
In a statement today, Samsung asked owners of the smartphones to exchange them for a loaner phone as it hammers out the terms of the recall.
"New Note7 replacement devices will be issued to exchange program participants upon completion of the CPSC process. In the interim, consumers can return their Note7 for another device," said Tim Baxter, the president of Samsung Electronics America. "Our collaboration with the CPSC, carrier partners and via our own communication channels is aimed at ensuring all Note7 users are aware of the issue and understand their options."
On Thursday the Federal Aviation Administration warned fliers not to put the Note7 smartphone in their checked bags or turn them on or charge them during flights.
The same day, Samsung and fire officials said they would be launching investigations after a Florida family said a Galaxy Note7 exploded in their Jeep on Labor Day, setting the vehicle on fire and destroying it. The family said that the phone had been left charging in the empty vehicle as the engine ran.
On Sept. 2, before the Florida incident, Samsung said it was suspending sales of and recalling the Galaxy Note7. The move came after several reports that the phones exploded while charging.
The tech giant said in a statement last week that there were 35 reported cases of phones with "a battery cell issue" and that it would replace devices that had been purchased. It also said sales of the smartphone would be suspended in 10 countries, including the U.S.
In February the FAA issued a safety alert about lithium-ion batteries, saying airlines that carried the batteries as cargo carried the "risk of a catastrophic hull loss" after they led to fatal fires on Boeing 747s in 2010 and 2011. In 2013 several fires in the batteries of Boeing 787s led the FAA to ground the entire Dreamliner fleet.
American Airlines announced Friday that it will start broadcasting warnings about the Samsung Galaxy Note7 at the gate, and on board flights. The gate announcement will be, "Due to a recall of the Samsung Galaxy Note7, the Federal Aviation Administration advises these devices should be powered off, and not connected to any power source while on board the aircraft. If your bag is checked at the gate, please remove your Galaxy Note7, and place it in your carry-on."
Samsung has sold more than 1 million Note7s since the smartphone debuted in August and has manufactured an additional 1.5 million units. The unsold devices will be replaced with new, modified versions so that they will not be affected by the battery problem, Samsung said.
ABC News' Paul Blake, Avianne Tan, and Erin Dooley contributed to this report.