One of four suspects held in the abduction and confinement of a teenager from Funabashi, Chiba Prefecture, has admitted digging a hole on a farm near Narita airport to bury her body, investigators said Monday.

Shota Nakano, 20, one of the suspects linked to the death of Manae Noguchi, 18, told police he dug the hole "the night before" burying her in the town of Shibayama. It is unclear exactly when she was buried.

Noguchi's body was found last Friday on the farm with her mouth covered by tape and her arms bound with zip ties, police said. Police are considering adding murder charges, given the possibility that she suffocated while bound.

Police have confirmed Nakano and another suspect, 20-year-old Yuki Ide, bought the ties at a do-it-yourself store in the prefecture. The pair and the other two suspects — a female 18-year-old and male 16-year-old — were in a rented car together when they abducted Noguchi on April 19 in the city of Chiba, investigators said.

Nakano and the 18-year-old female suspect allegedly beat Noguchi in the car's back seat, police said, adding that the 18-year-old had been a former classmate of Noguchi.

While Ide drove, the 16-year-old was in the passenger's seat, investigators said. The minor was quoted as saying he "heard groans in the back seat and was too scared to turn back."