British sprinter Nigel Levine has allegedly failed a drugs test, Press Association Sport understands.
The 28-year-old is understood to have tested positive for the banned asthma drug clenbuterol and is believed to be waiting for his B sample result.
Clenbuterol is on the World Anti-Doping Agency’s prohibited list because it is deemed performance-enhancing and can help weight loss.
UK Athletics do not comment on ongoing cases.
Levine, a 4×400 metre relay world champion, returned to training earlier this year after a serious motorbike accident with team-mate James Ellington in January.
He suffered a broken pelvis while Ellington also broke his pelvis and fractured his leg in two places when they were hit by a car.