LONDON — The IOC’s anti-doping chief acknowledged Wednesday he could have acted sooner to retest samples from the 2004 Athens Olympics to catch any drug cheats who escaped detection at the time.

IOC medical commission chairman Arne Ljungqvist was sharply criticized by senior IOC member Dick Pound on Wednesday for deciding only in May to retest about 100 samples from Athens. The International Olympic Committee is investigating up to five possible positive results from those retests.