INCIDENT China Southern A380 #CZ346 returned to Amsterdam yesterday because of a smoke detector indication

China Southern A380 B-6137 flight CZ346 from Amsterdam to Beijing was near Malmo Sweden when the captains received smoke detector indication and chose to divert to Hamburg.
The crew realised the indication was an error and returned to Amsterdam stating that this was not an emergency and no service or assistance was needed.
The aircraft arrived to Amsterdam 2 hours 15 minutes later with emergency services on stand by anyway.
The passengers said a siren began after the indicator was shown.
Firefighters boarded the aircraft on arrival and checked the plane.
Dumping fuel on the way back to Amsterdam