* The Ministry of Magic's Auror Department: This department is responsible for apprehending dark wizards and witches, which involves investigation and detective work.
* The Daily Prophet: The newspaper employs reporters who investigate and expose various crimes and magical happenings.
* Dumbledore's Army: While primarily focused on fighting Voldemort, Dumbledore's Army also gathers information and conducts surveillance on the Ministry of Magic.
* The Order of the Phoenix: Similar to Dumbledore's Army, the Order of the Phoenix is a clandestine organization that gathers information and conducts investigations, particularly against Voldemort's followers.
It's worth noting that the wizarding world is generally quite secretive and distrustful, so a traditional detective agency as we know it in the Muggle world may not be prevalent.