SAN FRANCISCO — Samsung said it is halting sales of the star-crossed Galaxy Note 7 smart phone after a spate of fires involving new devices that were supposed to be safe replacements for recalled models.

Separately, South Korean safety authorities said they found a possibility of a new product defect in the new Note 7 that may not be related to its batteries and urged consumers to stop using them. One of the safety officials said they have no idea when they could identify what caused the new Note 7 to catch fire.

“We would have not taken this measure if it had looked like things could end so easily,” Oh Yu-Cheon, a senior official at the Korean Agency for Technology and Standards that oversees product recalls, said in a phone interview. “It will take more time than we expected” to find the cause of the problems.

Oh said the investigators are looking into a new defect that is different from the one identified by Samsung in its earlier investigation of the first batch of Galaxy Note 7. Last month, Samsung said a tiny manufacturing error in the battery was to be blamed for fire. “The improved product does not have the same defect. That’s why we think there is a new defect,” Oh said.

In a statement issued late Monday, Samsung Electronics Inc. said consumers with original Note 7 devices or replacements they obtained after the recall should turn off the power and seek a refund or exchange them for different phones.

Officials from the U.S. Consumer Product Safety Commission echoed that advice in their own statement, adding that they are continuing to investigate at least five incidents of fire or overheating reported since a formal recall was announced Sept. 15.

“No one should have to be concerned their phone will endanger them, their family or their property,” said Elliot Kaye, chairman of the safety commission, in a statement. He called Samsung’s decision to stop distributing the device “the right move” in light of “ongoing safety concerns.”

NEW OVERHEATING INCIDENTS

The announcement follows several new incidents of overheating last week and deals a further blow to the world’s largest smart phone company. Leading wireless carriers have already said they would stop distributing new Note 7 phones as replacements for the earlier recall.

Samsung said it would ask all carriers and retailers to stop selling the phones and providing them as replacements for recalled devices. It said consumers should return their phones to the place where they purchased them. They can also get information from the company’s website.

Analysts say the new problems pose a crisis for the South Korean tech giant, which is locked in fierce competition with Apple and other leading smart phone makers.

“This has been a real black eye on the product,” said Ben Bajarin, a consumer tech industry analyst with the Creative Strategies firm.

A BLOW TO SAMSUNG

Analysts say the issue could hurt the company’s reputation and overall standing with consumers.

Samsung sells about a third of all high-end smartphones priced above $400, while Apple sells slightly more than half, according to investment analyst Kulbinder Garcha.