The Korean technology giant’s share price tumbled 7% in trading in Seoul on Tuesday, wiping billions of pounds off its value, as the future of the flagship handset was thrown into jeopardy.
The £740 smartphone was due to relaunch in the UK at the end of October after sales were delayed amid concerns that the mobiles were at risk of overheating or catching fire.
Samsung said it was confident it had overcome an issue with the devices’ battery after a reported 2.5 million handsets were recalled worldwide.
The manufacturer said it is “working with relevant regulatory bodies to investigate the recently reported cases involving the Galaxy Note 7”.
“Because consumers’ safety remains our top priority, Samsung will ask all carrier and retail partners globally to stop sales and exchanges of the Galaxy Note 7 while the investigation is taking place,” the firm added in a statement.
US officials said they were probing at least five incidents of fire or overheating reported since Samsung first recalled the devices in September.
Meanwhile authorities in South Korea said they had found a new product defect in the Note 7, but did not identify the issue.
Samsung said it remained “committed to working diligently with appropriate regulatory authorities to take all necessary steps to resolve the situation”.
“Consumers with either an original Galaxy Note 7 or replacement Galaxy Note 7 device should power down and stop using the device and take advantage of the remedies available.”
Authorities in the US and South Korea echoed Samsung’s advice to switch the phones off and not use them.
Analysts said the latest problems pose a crisis for the world’s largest smartphone company whose main rival, Apple, has seen its stocks surge.
The UK release date for the Note 7 had been moved to October 28 after Samsung ordered the recall following dozens of reports of devices overheating worldwide.
The firm then began a programme offering replacement phones to consumers who had pre-ordered the device in the UK.
The company said 45,000 Note 7s had been sold in Europe through the pre-order campaign - the majority in the UK - and more than 75% had since been replaced with either a Note 7 or another Samsung handset.
Samsung said in September that it was “confident” it had completely overcome the problem and was ready to launch the device.
However, concerns were raised over further defects beyond the battery cell, following several reports in the US of phones catching fire that showed the green battery icon Samsung added to replacement phones to mark them as safe.
Ben Bajarin, a consumer tech industry analyst with Creative Strategies, described it as a “real black eye on the product”.
In September Samsung saw £11 billion wiped off its market value when it first recalled the handset intended to take on Apple’s iPhone 7 plus.