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

The company ordered the suspension of sales on the recommendation of South Korean safety officials, who say they suspect a new defect in the replacement phones that may not be related to its batteries.

"We would have not taken this measure if it had looked like the problems could be easily resolved," Oh Yu-cheon, a senior official at the Korean Agency for Technology and Standards that oversees product recalls, said in a phone interview. He said it would take more time than the agency originally thought to figure out what's wrong.

In the meantime, the agency is urging consumers not to use the phones.

Last month, Samsung issued a global recall. It blamed a tiny manufacturing error in the battery that it said made the phones prone to catch fire.

Oh said the investigators are studying a different defect from the one Samsung said it had found in the first batch of Galaxy Note 7s.

"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 them off and seek a refund or exchange them for different phones.

Officials from the U.S. Consumer Product Safety Commission echoed that advice, saying they are investigating at least five incidents of fire or overheating reported since a formal recall in the U.S. was announced on 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."