Austin Bice mysteriously vanished after a night out in Madrid.
There are no solid clues as to his whereabouts, but the transatlantic search for him is expanding.
Bice's family members are in Spain to help with the search.
Bice's closest friends say they are sure there is something or someone preventing the 22 year old from contacting his family.
"This is completely out of character for him and he always would let someone know where he's going, especially in a foreign country," said Connor Fabiano, a friend.
Bice, who is an international business major and speaks fluent Spanish, had been studying in Madrid since January.
He was seen outside a nightclub the night of Feb. 25.
According to initial reports, Bice was allegedly turned away from the club for being too drunk. However, those who know him best say Bice is not a heavy drinker.
"I've known him for over a decade and I've never seen him drunk and I've never once seen him intoxicated to the point where he wasn't able to make a clear judgment or have a clear head," Fabiano said.
Alexis Gompf has known Bice since the fourth grade. The two were later high school sweethearts.
"He is not a partier and that's why everybody is so concerned," she said.
"They're just trying to find if he made a wrong turn," said Bice's mother, Pam. "They believe he's not thinking clearly. We don't know if he was drugged or if he was mugged, if he fell and hit his head."
Madrid investigators are examining the city's surveillance video, and Bice's father has traveled to Spain to help lead the search.
"I just want to say thank you for all being here," Larry Bice said. "It's hard for me to talk about it, but thank you.
The student's cell phone signal is still active, but his voicemail is full and there's been no activity on his credit cards.
"We just need to keep going and have all of those people look for him so we can get him home," Pam Bice said.
Bice's family has reportedly hired private investigators from San Diego to help search for their son.
The small team of investigators from the HALO Corporation is due to arrive in Madrid on Tuesday.
Bice was scheduled to return home to San Diego in June with only one semester of college left to obtain his degree.