Bloomberg is reporting that a 25-year-old customer from China, Hui Renjie, claims to have received a replacement Galaxy Note 7, and that it caught fire within 24 hours. A representative of the company immediately visited him and asked to take the phone to investigate, but the customer wished to go public first, assuming that he wouldn't get any answers if he just gave up the phone silently. The explosion allegedly caused minor burns to two of the customer's fingers, as well as damaged his MacBook.
Naturally, Samsung is very interested in what happened. The previous incident involved Samsung-developed batteries. The manufacturing process accidentally pushed some the battery batch's two terminals together. Shorting out a battery causes it to release energy quickly as heat, which is often undesirable, to say the least.
Samsung is waiting to examine the device before they comment further. If you have also receive a replacement, then you might want to keep it powered off and disconnected from the charger until we find out what happened.