Usage patterns
〈事〉が謎に包まれるfor something to be wrapped in mystery
That incident is still wrapped in mystery.
謎の〈人〉a mysterious (unidentified) person
A mysterious figure was standing in front of the station.
謎を解明するto clarify or get to the bottom of a mystery
The scientists are trying to unravel the mystery of that phenomenon.
謎めいた〈物〉something enigmatic or mysterious in nature
She wore an enigmatic smile.
謎が深まるfor a mystery to deepen
New evidence emerged, deepening the mystery even further.
Expressions
謎を掛けるpose a riddle · hint at; drop a hint