A 35-year-old Vittoriosa man was arrested on Friday morning after he was caught handing over a packet of heroin to prison inmates while they were in court, the police said.
A male prisoner, 39, was also investigated in connection with the case.
On Saturday morning, a 31-year-old Mellieħa resident was arrested after cocaine ready to be trafficked was found in his flat, along with other drug-related paraphernalia.
Magistrate Doreen Clarke is leading the inquiry. The three men are expected to be arraigned soon.