The airframers website indicates that Meggit supply the A330 engine fire detector loops.
That's another pneumatic type loop system. Similar systems have the brand names Systron-Donner, Lindbergh and Edison. (As a technical instructor, I currently teach this subject in my classroom.)
There are reports in several online news services that the fire indication was false, however I'd be hesitant to believe that until the engine, nacelle and fire detection system has been inspected and tested. A fire indication resulting from a bleed air leak is not a false warning since loop systems are overheat detectors. As previously mentioned, hot compressor bleed air leaks can cause allot of damage and/or start fires.
These loop systems are specifically designed to activate the fire/overheat alarm when they are subjected to either a localized or widespread overheat condition. In the case of a widespread or general overheat, the helium gas in the loop increases pressure as it's heated and activates a pressure switch in the responder unit, which activates the alarm. If the loop is subjected to higher temperatures, even in a localized area, hydrogen gas is released from the metallic core material, causing the pressure to rise and activate the pressure switch in the responder. If the loop then cools down, the pressure in the loop reduces, the switch opens and the alarm stops.
Most false alarms in pneumatic loop systems (and thermistor loop systems like the Kidde system for that matter) are caused by inadvertently misrouting the loop too close to heat sources like hot bleed air pipes. They are designed to be specific distances to the pipes and sometimes accidentally end up too close due to being bumped into during maintenance activities. There's really little else that can cause false alarms in pneumatic systems. (I have some experience investigating false alarms in my previous work as an A&P mechanic at a major business jet MRO)
For the bizjet types I've flown that are equipped with pneumatic fire loops, the engine fire in flight checklist calls for:
Affected engine - Idle thrust
If fire indication persists, shut down affected engine and activate fire handle/switch
If fire indication ceases, consider shutting down affected engine
If after shutting down engine and activating fire handle/switch, fire indication still persists, discharge button - PUSH
If fire indication persists after 10 seconds, fire second bottle
After fire indication ceases, Fire detection system TEST
The logic of this procedure is that at the end of the checklist, all that can be done has been done. If the system fails the test, then you don't know whether the fire still exists. You have to proceed with the assumption that you're still on fire! If after idling the engine the warning ceases, you may elect to leave the engine running at idle if deemed prudent. (after a satisfactory test the fire detection system of course)
So in this instance we do not yet know whether there was a fire, an overheat condition caused by a bleed air leak or a false alarm. The mechanics will isolate the cause through inspection and testing. If necessary, the engine can be run up and the bleed air system inspected for leaks.
Sorry it took so many words...