​AUTHORITIES at Ninoy Aquino International Airport (NAIA) have launched a comprehensive investigation following the discovery of a fetus at a sewage treatment facility at the main gateway. ​The fetus, approximately 8 months old, was uncovered by maintenance personnel during routine processing at the facility on Feb. 25. ​Initial reports indicate waste materials from an aircraft were brought to the treatment plant for disposal when cleaners found the remains. ​Security and medical personnel at the airport suspect the fetus was discarded by a passenger following an in-flight birth. ​Police theorize that an attempt was made to flush the remains down an aircraft lavatory, causing them to be consolidated with other waste during the plane’s standard cleaning and drainage cycle. ​Airport authorities are reviewing flight manifests and waste collection logs to trace the source. ​The investigation is focused on five flights from a local airline that arrived at Terminal 1 early Wednesday morning.