The Ducks are scheduled to open the 2020 season at home against Stanford on Nov. 7.
Oregon announced it did not scrimmage as scheduled on Saturday because of "five positive antigen tests within the program."
The Ducks said these were the first positives since daily testing began, and all who tested positive are asymptomatic, in isolation and being monitored by medical staff. Contact tracing is currently in process.
"I wish I had answers to some of the questions you might have; I don't," Oregon head coach Mario Cristobal said during a previously scheduled conference call with media timed for after the scrimmage. "I just wanted to provide you with transparency, let you know exactly where we are today.
"The scrimmage was canceled; tomorrow we are testing the entire team again, which is normal policy anyway, and (conducting) follow-up PCR tests for the other guys that had tested positive as well. And then from there, we'll see what the next steps are."
The 2019 Pac-12 and Rose Bowl champs opened preseason camp on Oct. 9, and they are scheduled to open the season at home on Nov. 7 against Stanford.