Bureau of Corrections (BuCor) Chief Benjamin delos Santos resigned from his post amid the resurgence of the drug trade in the New Bilibid Prison (NBP).
"Issue about resurgence of drug trade has made me irrelevant. My irrevocable resignation effective immediately was filed thru SOJ [Secretary of Justice]," delos Santos said in a text message.
On July 4, Justice Secretary Vitaliano Aguirre II ordered the National Bureau of Investigation to conduct a probe and case build-up on the "reported resurgence" of illegal drug trade in the NBP.
Members of the police Special Action Force (SAF) are under investigation over claims linking them to corrupt activities at the correctional facility, said Philippine National Police Chief Ronald dela Rosa.
Around 400 SAF troopers are manning the New Bilibid Prisons' maximum security compound and Building 14, where high profile inmates including convicted drug lords are detained.
President Rodrigo Duterte on Wednesday slammed the resurgence of the drug trade in the prison, saying it was aided by cellphones.