LONDON (AP) — At the midway point of the London Olympics, no competitor has been caught doping at their event. At least, not yet.

Still, every day a different name of a suspected offender has emerged because of an extensive pre-games testing program to target and identify the drugs cheats before they get near a venue.

On Saturday, a Colombian runner, a Brazilian rower and a Moldovan hammer thrower all made minor headlines — and all were not allowed to start their event.

Olympic officials think each case at this stage is a success in keeping the London Games clean. From here on, every positive doping result from an in-competition sample becomes more problematic for the Olympic image.