Morrisons supermarket in Aberystwyth had to close some of its tills, after tremors from a suspected sonic boom caused ceiling tiles to move.
The tills were closed briefly while staff checked for damage.
There have been other reports of rooms shaking, after many people heard what they thought was an explosion in the town.
More top news
Joyce Cox's body was found in woodland in Cardiff just after the outbreak of World War Two.
Glenys Thomas was using a walking stick when she was knocked to the floor by the bus.
Plaid Cymru complain after suggesting former leader Lord Dafydd Elis Thomas called their AMs "bunch of right wing of sh***" in the Senedd.