An iPhone 4 catching fire because of the USB port?

The image above was sent by an AT&T employee to the BGR with the explanation that the said iPhone caught fire at the bottom where the USB cable is connected to the phone and as you can see the flame melted the plastic around the cable and left burn marks on the phone. The person from AT&T claims that it is the first time he has seen something like this, but he received confirmation from an Apple Store that the problem with that iPhone 4 could be due to a faulty USB port. Does Apple know about the existence of such problems?

I've heard stories about iPhones/iPod Touches that caught fire, but this is the first time I've seen pictures of one that caught fire while connected to USB. The story seems to be true, however I remain reserved about its authenticity.