More than 30 rescuers are searching the South Rim after the 26-year-old Arizona State student disappeared between 27 and 28 April near Hermit Road.
Teams are using trail scans, walk-down routes, technical rope insertions, aircraft and drones, while investigators seek a person who turned in Krishna's black backpack at Bright Angel Lodge.
Krishna, an Indian master's student due to graduate on 9 May, had planned to return for exams and a job interview; his family has hired a private investigator and appealed for tips.
An ASU student vanished at the Grand Canyon, but his backpack was found. Who is the mystery person who turned it in?
Days before his graduation, a student went missing on the Rim Trail. Was it a tragic accident or something else?