Lucky them that it was something that cabin crew could take care of and contain it!
When I was a flight attendant for a major Asian airline, I once discovered a buzzing noise in the ceiling of the plane. It sounded like electrical circuit or wiring overloading (just my guesstimate). We called one of the pilots to see, but he was very reserved about it. Just advised to keep observing. Luckily nothing happened but we logged it before disembarking.