(CNN) -- A new search for an American teen who went missing on a mountain in Ecuador turned up no clues, the teen's father said Friday.
August Reiger has been missing since Sunday, when he went on a hike on a mountain overlooking the town of Banos. He was supposed to reunite with his family on the trail, but he was nowhere to be found.
Ecuadorian authorities have been searching for him for days, and on Friday, they once again scoured the mountain where he was last seen.
"There's nothing to tell, really," said his father, Chris Reiger. "We still don't have anything."
Search crews that have canvassed the mountain will do so once again to make sure he is not there.
Chris Reiger says the family hasn't ruled out the possibility of a kidnapping but adds that "none of this adds up. None of it."
August Reiger, who was his class valedictorian, has experience traveling abroad, including in his mother's home country of Syria, his father said.
"He's traveled so much before," Chris Reiger said. "We always went (to Damascus) every summer before the war broke out there. He's been to way more dangerous places than this."
Family members say it appears he vanished without a trace after they split up during a hike in the mountainous area 100 miles south of the capital, Quito.
Lira de la Paz Villalva, governor of Ecuador's Tungurahua province, said local authorities don't have any leads about what could have caused the teen's disappearance.
August had just graduated from the Classen School of Advanced Studies in Oklahoma City, said Shannon Schmoyer, Reiger's father's cousin. The 18-year-old had asked his parents for a trip to a Spanish-speaking country as a graduation present, she said.