Thirty-two medal winners at the world's six top city marathons were among the hundreds of long distance runners with suspicious blood test results revealed in a leak, a newspaper reported on Sunday.
The leaked blood tests have jolted the world of international athletics since a German broadcaster and a British newspaper first published reports about them a week ago.
Britain's Sunday Times and Germany's ARD say the results from the database of the sport's governing body, the International Association of Athletics Federations (IAAF), show evidence of widespread cheating among long distance runners.
Last week, the news organisations said the data showed that between 2001 and 2012 a third of Olympic and world championship endurance and middle distance running medals had been won by athletes who, at some point in their careers, had given a suspicious blood test.
The Sunday Times said many of the suspect runners had also won medals in the six most prestigious city marathons: in Berlin, Boston, Chicago, London, New York and Tokyo.
Seven of the 24 men's and women's winners of the London marathon between 2001 and 2012 were athletes who at some point in their careers had produced a suspicious blood test result, the Sunday Times said. It has not named the athletes.
Last week, the IAAF stripped Russian runner Liliya Shobukhova of all her medals since 2009, including three victories in the Chicago marathon and one in London.
The London marathon said in a statement on Sunday: "We continue to be at the forefront of anti-doping measures for marathon runners as we are determined to make marathon running a safe haven from doping but we cannot do it all on our own and rely heavily on the IAAF.
"We are therefore very concerned by the allegations made in the Sunday Times today and we will be discussing the implications of the allegations with the IAAF."
The Sunday Times and ARD say their information comes from more than 12,000 blood tests of 5,000 athletes, 800 of whom have had at least one "abnormal" result at some point in their careers.
The IAAF, which has defended its drugs testing procedures strongly and refutes suggestions it has turned a blind eye to doping, says it is cooperating with the independent World Anti-Doping Agency (WADA) in an investigation into the allegations.
