He has been identified as a 45-year-old from Nalluruwa, Panadura, Police Spokesman DIG Ajith Rohana stated.
In the meantime, the finance manager of the relevant website has also been taken into custody by the law enforcement authorities.
The 43-year-old is a resident of Alubolanda area in Mawiththara, Piliyandala.
The two arrestees are expected to be produced before the court later today (July 04).
According to the police, a total of 28 suspects are currently under arrest over the said sex-trafficking ring.
Reportedly, the mother of the victimized teen, the vice chairman of Mihintale Pradeshiya Sabha, vehicle drivers, the man who designed the advertisement and a saffron-robed person, a captain of a ship, several crew members and a gem merchant are among the arrestees.
The incident first came to light during an investigation into a person arrested in Mount Lavinia on June 07.
The officials uncovered that the main perpetrator had posted several advertisements online and sold the teen to third parties for a period of three months.
Investigations are under way in search of 16 other suspects who are linked to the crime, the police said further.