According to European Commission spokeswoman Helen Kearns
Apple have come back to us ... and what they've said to us is that they consider these are isolated incidents. They don't consider that there's a general problem.
We are aware of these (media) reports and we are waiting to receive the iPhones from the customers. Until we have the full details, we don't have anything further to add.
There are no specifics concerning which generation of iPhone Apple is investigating as this issue stems back at least the the iPhone 3G when an iPhone owner was burned by his device.