Triple Olympic champion Usain Bolt has conceded that revelations five fellow Jamaican athletes have tested positive for a banned substance will place all competitors under the spotlight.
The athletes - four men and one woman - are not thought to be any of the Olympic medal winners from last summer's Games in Beijing.
'It's sad for the sport because the sport was getting on so well, I was trying to bring it back,' said Bolt after winning the 100 metres at last night's Aviva London Grand Prix in 9.91 seconds.
'This is probably a step backwards because people start questioning everybody, especially from Jamaica. For me it doesn't matter because I will be going out there, day after day, doing my best. I get tested all the time. It shows that people get tested and they get caught if they are on drugs.
'Sometimes you move forward and you take one step back. It's hard but I'm trying my best to push the sport forward. I think after a while people will notice that you can't get away with it and they'll stop, but for now I guess we can't do anything about it.
'I'm not sure who it is yet, I'm sure it's not me so I'm not really worried. If it's someone from my group I don't know, I can't comment.'
Former world record holder Asafa Powell added: 'It's their bad luck, it's not for me to worry about, it doesn't affect me one bit. People might be saying bad stuff now but it doesn't really bother me.'
The International Association of Athletics Federations (IAAF) had earlier confirmed news of the positive tests.
IAAF spokesman Nick Davies said: 'We have just received the paperwork from Jamaica, it is five - four guys and one girl. These are in-competition tests.
'We now inform the (Jamaican) federation who will then inform the athletes and then they are asked if they want the B sample tested. It's very, very early in the process so we cannot say who they are or what the substance is.'
Aleen Bailey, who competed in the women's 200m in London, was visibly shocked by the news.
'You never want anybody from your country or your team to be tested positive,' she told BBC Sport.
'Hard work takes you a long way and if somebody cheats they deserve to be punished. But hopefully it's not anything serious and it's a mishap. Hopefully it can be sorted out.
'We don't want any cheaters in the system. It hurts when it's someone from your country.'
