Both the Baton Rouge police department and Collins' representatives confirmed the results.
Collins was interviewed by police Monday about the shooting death of a 29-year-old pregnant woman in Baton Rouge, Louisiana. Brittney Mills, Collins' ex-girlfriend, was shot to death April 24 upon opening the front door of her home.
Mills' unborn child survived the shooting but died a week later in the hospital.
Police said Collins is not a suspect in the case, nor even a person of interest.
Collins' representatives also told ESPN's Josina Anderson that Collins passed the polygraph test administered by an independent investigator in connection with Mills' case.
Collins, who was once seen as a likely first-round selection, was not selected in the last week's draft and is now classified as an undrafted free agent and, despite his original intention to do so, cannot re-enter the 2016 draft, a league spokesman told ESPN NFL Insider Adam Schefter.