A Sofia police investigator was arrested while taking a bribe, the Interior Ministry said. He works for the Sofia Directorate of the Interior (SDVR).
The ministry's Internal Security Directorate had planned the operation in advance.
Officers found marked banknotes on him.
The ministry's early findings say he promised to influence a pre-trial case, which he was leading himself, in return for the money.
The ministry said work to establish the full facts of the case continues.