The CBI has arrested an alleged co-conspirator in the NEET-UG paper leak case, Aman Singh, from Dhanbad in Jharkhand, officials said on Wednesday. The agency had earlier arrested the principal and vice principal of the Oasis school in Hazaribagh. Two others were also arrested for allegedly providing the place to the NEET candidates from where the burnt question papers were recovered by Bihar Police. The CBI has registered six FIRs in the case. The FIR from Bihar pertains to the leakage of paper while the remaining from Gujarat and Rajasthan pertains to impersonation of candidates and cheating.