Chinese parents receive a ransom note for the missing 17-year-old foreign exchange student in Utah

Chinese national Kai Zhuang was formally reported missing on Friday, and according to the police, there is "reason to believe" that he is "being held against his will." 

Authorities in Utah are searching for a 17-year-old foreign exchange student who vanished from the house he was staying in with his host family on Thursday. 

The Utah Department of Public Safety said that the teenager was last seen in Riverdale, which is around 30 miles north of Salt Lake City, at around 3:30 a.m. local time. 

China's Kai Zhuang was formally reported missing on Friday, and authorities have informed media outlets that they have "reason to believe" that Zhuang is "being held against his will." When USA TODAY asked for comment on Friday, the department did not answer right away.

Kai is characterized as 150 pounds, 5 feet, 6 inches tall, with dark eyes and black hair. Though police claim he frequently wears a green jacket, it's unknown what he was wearing when he was last spotted.