The second round of fires, which affected the devices sent to replace the original faulty phones, were caused by several manufacturing issues, including inadequate welding at the battery manufacturer, as the company raced to produce those new phones.

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“We are committed to earning the trust of our customers through innovation that redefines what is possible in safety, and as a gateway to unlimited possibilities and incredible new experiences,” DJ Koh, Samsung's president of its Mobile Communications Business, said in a statement. The company said 96 percent of Galaxy Note 7 phones have been returned.

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On stage during a news conference in Seoul, Koh was quick to point out that several of the phone’s key design features — including its iris scanner, fast-charging feature and USB-C port — had not caused the fires.

The U.S. Consumer Product Safety Commission, which administered the recall in the United States, declined to comment on the report. At least 96 fires have been reported in the United States — including a car fire in Florida that brought widespread attention to the problem. The phones are banned by the Federal Aviation Administration. The phones are so volatile that airline staff were instructed to announce that ban at the start of every flight — a requirement that was lifted Jan. 10.

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The report was compiled by Samsung and third-party researchers it hired to work on the investigation. The issues disclosed Sunday ultimately led the company to issue two recalls for its flagship Galaxy Note 7 smartphone, and to stop making the device altogether. Samsung recalled about 2.5 million phones.

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The recall was damaging for the company, which reported its lowest profits in years in the quarter immediately after the recall. Sales numbers also indicate that it lost ground to its smartphone rival Apple over the crucial 2016 holiday season. Analysts have estimated that Samsung may have lost as much as $10 billion because of the recall, in costs and lost sales. Samsung will report earnings this week.

Samsung officials said they “have taken several corrective actions to ensure this never happens again, including the implementation of a multi-layer safety measures protocol at the product planning stage, and an 8-Point Battery Safety Check.”

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The extra safety checks add several new tests for Samsung and its manufacturers. The company said it will increase the rigor and frequency of visual tests — including an X-ray — to look for problems in the shape and size of its batteries. Both battery manufacturers and Samsung will disassemble the batteries as part of these checks, to avoid issues such as the welding problems that cause the second round of fires.