The 200m world champion, Veronica Campbell-Brown, has reportedly tested positive for a banned substance.

The 31-year-old is the most decorated female Jamaican athlete in history but reports in her homeland on Saturday claimed that a banned diuretic had been found in her system at the Jamaican International Invitational meeting in Kingston on May 4.

Campbell-Brown, who won Olympic gold at the 2004 Games in Athens and at Beijing in 2008, could face a two-year ban if her sample for the masking agent furosemide is confirmed. Campbell-Brown was said to be present at the World Anti-Doping Agency headquarters in Montreal last week to be shown the results of her B sample.

When contacted by the Observer on Saturday, the International Association of Athletics Federations would not comment on the allegations, although the WADA code lists furosemide, taken as the pill Lasix, on its list of forbidden substances.

On Saturday night, the president of the Jamaican Athletics Administrative Association, Warren Blake, confirmed that a major name among the country’s sprinters had failed a doping test and that they were awaiting the results of a back-up sample.

Furesomide, taken to promote the production of urine and help high blood pressure and used in the treatment of congestive heart failure, is known as a masking agent because it can hide traces of other illicit substances in a person’s body that boost performance.

To avoid a suspension she would have to explain to WADA that there are exceptional circumstances around her sample, although the anti-doping body operates a policy of strict liability where ignorance to the substances inside an athlete’s body is no defence.

A two-year ban would rule her out of defending her world title in Moscow later this year. Reports in Canada suggested she has withdrawn from the Edmonton International Track Classic, scheduled for June 29.

Campbell-Brown won gold in Daegu two years ago and also picked up a silver medal with Jamaica in the 4x100m relay at London 2012. She finished fourth in the final of the women’s 200m in London, having competed in the same preliminary heat as Cambodia’s Chan Seyha.

If her test is confirmed it would arguably be the biggest international scandal since the American Marion Jones confessed to doping in 2007 and was subsequently stripped of her Olympic medals. It would also plunge Jamaican athletics into deep uncertainty after the country’s high levels of success in recent years.

Only last week the island’s 400m runner Dominique Blake received a six-year ban for her second doping offence since 2006, the Jamaica anti-doping disciplinary panel issuing the suspension after she tested positive for the stimulant methylhexanamine at last year’s Olympic trials.

Additional reporting by Dan Riley