In both instances "engine damage" occurred which then led to a fire, thought to be caused by oil spilling onto hot components.
A total of 785 of Porsche's high-performance variant of the 911 have been delivered so far this year. The two cars affected were based in Italy and Switzerland respectively; no accidents or injuries resulted from the incidents.
The company's engineers are currently working to identify the fault, after which any necessary revisions will be made to the remainder of the cars at Porsche dealerships.
As well as contacting existing customers, those that have not yet taken delivery are being made aware that there may be a slight delay in the arrival of their new 911 GT3 while the circumstances surrounding the failures are investigated.
Porsche has said that it will report on any new findings immediately.