An 18-year-old Clatskanie man was arrested Friday on allegations he had engaged in sexual activity with an underage girl he met online.

The investigation commenced in October 2016 when Clatsop County Sheriff’s Office (CCSO) received a report from the mother of an area 14-year-old girl.

The mother discovered information from a social media site showing her daughter was in contact with Theron Joseph Manley, 18, of Clatskanie.

Theron Joseph Manley, 18, of Clatskanie, Ore., was arrested Jan. 13, 2017 concerning sexual allegations involving an underage girl. Photo courtesy of Clatsop County Sheriff’s Office

Subsequent investigation indicated Manley was pressuring the girl to transmit nude images of herself to him, and attempted to make plans to meet with the girl for sexual activity.

It was also learned during the investigation Manley did meet with the girl on one occasion in October in the city of Warrenton for sexual activity.

CCSO also obtained evidence indicating Manley used the same social media site to set up meetings with other girls between ages 13 to 15 in the Warrenton and Seaside areas. These proposed meetings were also allegedly for the purpose of sexual activity.

Additionally, evidence from the social media site indicated Manley also used the site to make arrangements to bring marijuana to teenagers in the same areas.

CCSO is continuing to investigate this case, and ask anyone who knows of any other possible victims or has any information to contact Detective Ryan Humphrey at the Clatsop County Sheriff’s Office.

Manley was arrested Jan. 13, 2017 by the Pacific County, Washington Sheriff’s Office on behalf of Clatsop County Sheriff’s Office. He was extradited to Clatsop County that day and is lodged on three counts of first-degree online sexual corruption and two counts of attempted use of a child in sexual display.