open enquiries and secret search (idiom); to investigate openly and in secret
taking information from all sides
Definitions (粵典–words.hk)
動詞
表面上公開調查，暗中又另有訪問搜查 to investigate, openly and secretly
就住中國啲黑心食品，佢已經明查暗訪咗三年。
就住中国啲黑心食品，佢已经明查暗访咗三年。
zau6 zyu6 zung1 gwok3 di1 haak1 sam1 sik6 ban2, keoi5 ji5 ging1 ming4 caa4 am3 fong2 zo2 saam1 nin4. He has been investigating, openly and secretly, the adulterated, tainted food in China for three years.
戰亂之後，佢明查暗訪，希望揾返失散咗嘅太太。
战乱之后，佢明查暗访，希望揾返失散咗嘅太太。
zin3 lyun6 zi1 hau6, keoi5 ming4 caa4 am3 fong2, hei1 mong6 wan2 faan1 sat1 saan3 zo2 ge3 taai3 taai2. After the war, he observed openly and investigated secretly, hoping that he could find his lost wife.
參看
明查暗訪
Definitions (Wiktionary)
verb
to observe publicly and investigate privately; to conduct a thorough investigation