The British Olympic boxer Muhammad Ali is facing a lengthy ban after testing positive for a steroid in April, the amateur sport’s international federation, Aiba, has confirmed.

It is the first time since GB Boxing was established in 2008 that one of its fighters has tested positive. The news was met with shock and dismay at the GB Boxing headquarters in Sheffield, which has seen Nicola Adams, Anthony Joshua and James DeGale progress through its ranks.

Ali’s positive test came during a World Series of Boxing match between the British Lionhearts and Morocco Atlas Lions in Casablanca and, when notified in May, GB Boxing immediately suspended him from their programme.

The 21-year-old was the youngest Team GB boxer to compete at the Rio Olympics. He lost in the first round of the flyweight competition but the 2016 European Championships silver medallist is highly rated by coaches and was aiming to be selected for the 2020 Olympic Games in Tokyo.

It is understood Ali was tested six times in the year to March 2017 and did not return any adverse findings.

It is believed Ali asked for his B sample, which is used to confirm an initial finding, to be tested and that came back positive for trace amounts of the steroid.

GB Boxing, which won three medals in Rio, has a full-time nutritionist and prides itself on providing fighters with a rigorous anti-doping education. It is understood that between May 2015 and December 2016 Ali took part in four anti‑doping education sessions delivered either by GB Boxing or the UK Anti-Doping Agency.

Although he trained in Sheffield four days a week it is believed Ali also trains at his home gym in Bury, under Amir Khan’s former coach Mick Jelley. Ali, who was named after the man considered to be the greatest boxer of all time, was almost forced to give up boxing in 2012 when his younger brother Danish, also a talented boxer, suffered a brain haemorrhage. He credits the sport with helping him avoid being drawn into gangs.

A GB Boxing spokesperson said: “GB Boxing can confirm that a member of its squad has tested positive for a banned substance. The boxer is suspended from the GB Boxing squad pending the outcome of the process. The boxer has also been suspended from all international and domestic competitions, in accordance with the provisions of the World Anti‑Doping Agency and the International Boxing Association, until this process is finalised.

“This is the first time that a member of the GB Boxing squad has tested positive for a banned substance. GB Boxing is committed to clean sport and we work in partnership with UK Anti-Doping and our International Federation to provide extensive education and support to our boxers on anti-doping rules, the anti-doping obligations upon them as athletes and the importance of adhering to the principles of clean sport.”