According to the NHTSA website, investigations were announced on Saturday. Out of the 12 registered complaints, eight of the fires occurred while the cars were parked without the engines running. Specific models included 2007 and 2008 MINI Cooper S variants, and could affect around 36,000 owners in the US.
At this stage of the investigation, the specific cause of the fires is unknown, with some suggesting it could be down to an oil leak in one of the lines connected to the 1.6-litre four-cylinder's turbocharger. If there was an oil leak in this area, it could potentially drip onto the extremely hot exhaust system, causing a fire.
It seems the complaints have increased more recently. An NHTSA regulator said in a recent Automotive News report that "complaints show an apparent increasing trend with most complaints received within the past year".
Results of the investigation are expected to uncover the possible problem in any case. There is also the possibility that BMW and MINI could announce a recall prior to the results being announced.
There are no known reports of such spontaneous fires taking place in Australia.