Doping has come back to haunt Indian athletics with two top women quarter-milers returning positive for a banned substance in tests conducted by the International Association of Athletics Federations.As per a NADA source, the 'A' samples of the two 400 metre runners taken by an international agency — International Doping Tests and Management of Sweden — on behalf of the IAAF at NIS Patiala and tested at National Dope Testing Laboratory in New Delhi had returned positive for prohibited substance. One of the two was a member of the women's 400 metres relay quartet that had won gold in the Commonwealth Games last October and in the Asian Games in Guangzhou last November. The other had missed out a podium finish in the 400 metre race in the Asian Games.The banned substance is expected to be revealed only bafter 'B' sample test results.Both the athletes had their 'B'samples tested on Monday at the NDTL.The development is a huge setback for the country as both were in the yet-to-be-announced Indian team for the AsianAthletics Championships to be held in Kobe, Japan from July 7.