EUGENE, Oregon (AP) — Back-to-back NCAA champion Randolph Ross was booted from the world track and field championships on the eve of his 400 meter preliminary race, about a month after officials could not locate him to take an antidoping test.

The Athletics Integrity Unit announced Saturday it was provisionally suspending the North Carolina A&T sprinter for tampering with the antidoping process after an unsuccessful testing attempt on June 18. The investigation concluded, the AIU said, after officials interviewed him Thursday.

Also ousted from the meet was Kenyan marathoner Lawrence Cherono, who tested positive for a banned substance used to treat chest pain resulting from lack of blood supply and oxygen to the heart. It was the same drug that led to Russian figure skater Kamila Valieva’s doping case at the Beijing Winter Olympics this year.

Both athletes had been scheduled to compete Sunday.

The AIU said there were delays in the processing of Cherono’s test sample, which was taken May 23, that made it impossible for another Kenyan to take his spot.

Ross won his second straight title in the 400 meters at NCAA championships earlier this year,

Athletes are required to give antidoping authorities detailed lists of where they’ll be so testers can reach them with no notice to collect samples when the athletes are not competing. In some cases, three missed tries can result in an antidoping violation. AIU did not release the specifics of Ross’ case, other than to say “the allegation arises out of the athlete’s conduct during the course of an investigation into a potential whereabouts violation.”