The U.S. Consumer Product Safety Commission says owners of the Galaxy Note 7 smartphones should turn them off and stop using them because of the risk that their batteries can explode.
The agency also says it's working with Samsung on an official recall of the phones "as soon as possible" and that it's trying to figure out if the company's replacement Note 7s are an "acceptable remedy."
Last week, Samsung ordered a global recall of the jumbo phones after its investigation of explosion reports found the rechargeable lithium batteries were at fault. In one case, a family in St. Petersburg reported a Galaxy Note 7 phone left charging in their Jeep caught fire, destroying the vehicle.
In a statement Friday, Samsung says Note 7 owners should shut off their phones and exchange them now for another device. But the company says new Note 7 phones will not be available until after the CPSC finishes its "process."
On Thursday, U.S. aviation safety officials took the extraordinary step of warning airline passengers not to turn on or charge the Galaxy Note 7 phones during flights.
The Federal Aviation Administration also warned passengers not to put the smartphones in their checked bags, citing "recent incidents and concerns raised by Samsung" about the devices. It is extremely unusual for the FAA to warn passengers about a specific product.
Samsung launched the latest version of the Note series in August. The Note series is one of the most expensive lineups released by Samsung, and the devices usually inherit designs and features of the Galaxy S phones that debut in the spring. Samsung also added an iris scanner to the Note 7, which detects patterns in users' eyes to unlock the phone.
Before the issue of battery explosions emerged, supplies were not keeping up with higher-than-expected demand for the smartphone.
The Note 7 isn't the only gadget to catch fire thanks to lithium-battery problems, which have afflicted everything from laptops to Tesla cars to Boeing's 787 jetliner.
Rechargeable lithium batteries are more susceptible to overheating than other types of batteries if they are exposed to high temperatures, are damaged or have manufacturing flaws. Once the overheating starts, it can lead to "thermal runaway" in which temperatures continue escalating to very high levels. Water can put out the flames, but doesn't always halt the thermal runaway. Flames will often reappear after initially being quenched.
Lithium batteries have become ubiquitous in consumer electronic devices. Manufacturers like them because they weigh less and pack considerably more energy into the same space than other types of batteries.
Earlier this year, the International Civil Aviation Organization, a U.N. agency that sets global aviation safety standards, banned bulk shipments of rechargeable lithium-ion batteries as cargo on passenger planes until better packaging can be developed to prevent a fire from spreading and potentially destroying the plane.