LINCOLN, Neb. (AP) — University of Nebraska-Lincoln officials say Chinese authorities have detained an assistant business professor who is a Chinese citizen.

University spokeswoman Kelly Bartling said Monday that a family member told school officials late last week that Weixing (WAY’-shing) Li was in Chinese custody. She said the university is trying to verify Li’s whereabouts, but doing so can be difficult.

Bartling said university officials don’t know why he was detained. She declined to identify the family member who notified them, saying the person had asked not to be named and did not want to speak with reporters.

Li has taught at UNL since 2003. Bartling said he was leading 18 students on an annual study-abroad program, and some students became concerned after he stopped returning their emails.