Ivaylo Vasilev, chief of a Sofia police unit, and six other members of his unit were indicted on charges of bribery and blackmail, the State Prosecutor's Office said.
The charges were filed on July 31, a day after the seven member of the Sigma motorcycle patrol unit at the Sofia Police Directorate (SDVR) were arrested.
Prosecutors allege they were involved in an organized criminal gang which has been active since January 2013, according to the website Dariknews.bg.
The group's members are said to have forced drivers who committed traffic offenses into paying hefty bribes in order to avoid other sanctions.
Vasilev is in 72-hour detention that started on Tuesday evening, and the Specialized Prosecutor's Office will demand that he remain in custody. The other six were released after each of them was imposed a BGN 500 (EUR 250) bail.
Sigma policemen are responsible for maintaining public order, carrying out investigations, escorting criminals to court or to an airport in case of an extradition.
Among those escorted was Serbian drug lord Sreten Josic, who was extradited to the Netherlands in 2002 after Interpol issued an arrest warrant.
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