Who prosecutes election-related criminal offences?

Article261 paragraph (2) Law No 8/2012 on Legislative Election

(1)   In the event that theinvestigation results are incomplete, the public prosecutor shall return thecase file to the investigator of the State Police of the Republic of Indonesia,  in no later than 3 (three) days alongwith instructions concerning actions that need to be done for the completion.

Source: http://aceproject.org/electoral-advice/archive/questions/replies/286046320/230159556/Unofficial-Translation-of-Law-8-2012-on.pdf