Former chief of the National Intelligence Service(NIS) Lee Byung-kee has been detained over allegations that the spy agency delivered money to key aides of ex-President Park Geun-hye while she was in office. 
 
The Seoul Central District Prosecutors' Office said it took Lee into custody early Tuesday while questioning him, "considering all circumstances" surrounding its investigation.
 
The prosecution, which can hold a suspect for up to 48 hours without a court-issued arrest warrant, will determine before the deadline whether to apply for a formal warrant for Lee.
 
Lee is one of three former NIS chiefs who are accused of illegally providing a total of around four billion won of the agency's funds to close aides of Park between 2013 and mid-2016.  
 
Lee's predecessor, Nam Jae-joon reportedly admitted to sending about 50 million won to the presidential office every month. 
 
The prosecution confirmed on Monday during questioning that the amount of the monthly payment was raised to 100 million won during Lee’s term. 
 
Prosecutors also grilled Lee on whether the monthly payment affected his appointment as chief presidential secretary.
 
The prosecution believes Lee is the key figure to get to the bottom of the bribery structure between the spy agency and the presidential office as he gave as well as received the monthly payments.