The four students were found dead in a home on Sunday near the university campus.
"Although no weapons have been located, based on preliminary information, investigators believe that an edged weapon such as a knife was used," police said in a news release.
Autopsies are scheduled to be completed later this week, and police hope that will provide more information about the deaths.
Moscow Police said they "believe this was an isolated, targeted attack and there is no imminent threat to the community at large."
Investigators are working to establish a timeline of events on the evening of Nov. 12 and the early morning of Nov. 13.
This time period falls hours before police were called to the home.
Moscow Police received a call just before noon on Sunday about an unconscious person at King Road.
KREM TV reports when police arrived on the scene, they found four people dead in the home.
Police do not have any suspects in custody, but said they are following leads and "identifying persons of interest."
Anyone with information is asked to contact the Moscow Police at 208-883-7054.
The University said a vigil for the students which was scheduled for Tuesday night will be postponed until after fall break.
The victims have been identified as:
- 20-year-old Ethan Chapin from Conway, WA.
- 21-year-old Madison Mogen from Coeur d'Alene, ID.
- 20-year-old Xana Kernodle from Post Falls, ID.
- 21-year-old Kaylee Goncalves from Rathdrum, ID.