Sisi Xin (28), a dietetics student based in Christchurch, was last seen in the suburb of Avonside with her friend, Didem Yaman (31), a Dunedin politics PhD student, who is also missing.
Both have been reported missing to the Red Cross and police.
Ms Yaman's friend, Sumana Islam, yesterday said the pair were seen by a neighbour, who believed they were heading to the central city, about 11.30am.
"We have very serious concerns for her safety," she said.
Fellow friend James McIlraith said "with the time periods that pass, there is growing doubt as to their wellbeing".
He described her as a "warm, compassionate, wonderful human being" and the past week had been a "very difficult time for those who love her".
Her family in Turkey maintained hope she would be found alive, but the situation was "growing darker by the day".
Ms Yaman, a Turkish national, is described as 165cm tall, of slim build, with red, curly, shoulder-length hair and pale skin.
Gamze O'Neill said many of her friends had travelled to Christchurch to search for her and liaise with authorities, to no avail.
"Her family in Turkey are praying for her safe return, as are we," she said.
"They have not been heard from since," he said.
The Chinese national is 167cm tall with shoulder-length black hair, and was last seen wearing a summer dress and a golden pendant with her name on it.
If anyone had seen Ms Xin, Mr Low would like to hear from them.
He can be telephoned on 021 222 9549.
University director of student services David Richardson said the university was "deeply concerned" about the welfare of the pair.
"University staff are liaising closely with police and the students' family and friends to provide them with as much support and assistance as possible at this difficult time," he said.
University of Otago officials do not know yet when its buildings in Christchurch will be fully assessed and repaired or when classes will resume, vice-chancellor Prof Sir David Skegg said on the university's website yesterday.
The university's main building in Christchurch, the Christchurch School of Medicine attached to Christchurch Hospital in Riccarton Ave, was damaged in one area, he said.
It had been yellow-stickered, meaning only essential staff could enter.
Consulting engineers carried out another inspection yesterday morning and it was hoped they would quickly establish a programme for completion of the repairs and reoccupation of the building, he said.
The university also had departments and programmes in several other buildings within the cordoned-off exclusion zone which had been unable to be assessed yet, he said.
Classes have been suspended until at least next Monday.
About 800 students study at the Christchurch campus.
Staff were in touch with them daily via mass texts, a university spokeswoman said.
