RIO DE JANEIRO (Reuters) - Bulgarian runner Silvia Danekova has tested positive for a banned substance and has been temporarily suspended pending the test of her B sample, two sources familiar with the case told Reuters on Thursday.

The 33-year-old, who was due to compete in the women's 3000m steeplechase, tested positive in a doping control conducted in Rio a few days after her arrival in Brazil on July 26, the sources said a day before the athletics programme begins.

According to the same sources, Danekova, who raced the steeplechase at the London Olympics in 2012 but did not get beyond the heats, used the banned blood booster erythropoietin (EPO).

Neither Danekova nor her coach Rumen Angelov were immediately available for comment.

"Unfortunately, we have a positive test," Bulgarian Olympic Committee's Secretary General Belcho Goranov told local media, refusing to name the athlete who tested positive. "We expect the opening of the B sample test."

Bulgarian athletics has been marred by a series of doping offences recently while its weightlifting team was banned from Rio for doping.