Miles is under investigation for sexual harassment and inappropriate behavior with students while at LSU in 2013. The former Tigers head coach was reportedly banned from contacting female students at the school.
"Today, I placed head football coach Les Miles on administrative leave as we conduct a full review to determine the appropriate next steps," Long said.
"Even though the allegations against him occurred at LSU, we take these matters very seriously at KU," he added. "Now that we have access to this information, we will take the coming days to fully review the material and to see if any additional information is available. I do not want to speculate on a timeline for our review because it is imperative we do our due diligence. We will be able to comment further once our review is complete."
Miles is accused of "texting female students, taking them to his condo alone, making them feel uncomfortable, and, on at least one occasion, kissing a student and suggesting they go to a hotel after telling her he could help her career."
An internal investigation released Friday showed former LSU athletic director Joe Alleva recommended the program fire Miles for "inappropriate behavior" in 2013. The university suspended two athletic officials for not reporting the misconduct allegations at the time.
Kansas named Miles its head coach in November 2018. He posted a 3-18 record over the last two seasons.
The 67-year-old coached at LSU from 2005 to 2016 and had a short stint at Oklahoma State (2001 to 2004).
Offensive coordinator Mike DeBord will lead the Jayhawks with Miles on leave, sources told ESPN's Chris Low.