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How Do Samsung Galaxy Note 7 Phone Batteries Explode?

Samsung Battery Recall Draws More Attention to Smartphone Fires 1:57

Samsung earlier this week announced a worldwide recall on its Galaxy Note 7 smartphone after the phone caught fire in several high-profile incidents due to battery issues.

Although the company never used the word "recall" in its announcement, the message was clear: the company has not yet figured out what's causing the Lithium-Ion batteries to catch fire.

The recall prompted several mail carriers and shipping companies to institute strict guidelines about how to transport the phones back to the company.

And the episode has also prompted greater public oversight into the issue of battery fires and the dangers they pose to public safety.

NBC News was granted rare access inside the Underwriters Laboratories in Chicago to view their special battery testing lab, where we received an up-close look at how batteries explode.