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 criticised by senior IOC member Dick Pound today for only deciding in May to retest about 100 samples from Athens.

The International Olympic Committee is investigating up to five possible positive results from those retests.

Pound, former chairman of the World Anti-Doping Agency, expressed ‘‘concern and disappointment’’ about the IOC’s reluctance to retest earlier — an unusual public rebuke during the IOC’s general assembly.

‘‘The keeping of samples was meant to be a major deterrent,’’ Pound said. ‘‘If those we hope to deter understand we do nothing, there is not going to be much of a deterrent.’’

‘‘If we’re going to live up to our objective of zero tolerance in doping, we have to take advantage that we have all these samples and take the opportunity to retest them,’’ he added.

Pound also complained that the IOC had only decided to carry out the retests after pressure from the media and WADA.

Ljungqvist agreed the IOC could have moved sooner but said the committee had no evidence that any banned substances used in Athens hadn’t already been tested for at the time.

‘‘I admit we could have done it a little earlier,’’ he said.

The IOC stores doping samples from each Olympics for eight years to allow for retesting. The statute of limitations for Athens will expire Aug. 29, the date the games closed in 2004.

Ljungqvist noted that the IOC did test samples retroactively from the 2008 Beijing Olympics and 2006 Winter Games in Turin to check for the use of blood-boosting drug CERA. Those retests led to five new positive cases from Beijing — including the stripping of Rashid Ramzi’s gold medal in the 1,500 meters — but none from Turin.

‘‘With respect to the Athens Games, there was no information that any substance would have been in use that was not already analyzed for,’’ Ljungqvist told Pound. ‘‘We waited quite a while. The idea came up I admit quite late.’’

He said today’s testing methods are ‘‘more sophisticated and sensitive’’ than they were eight years ago.

‘‘Had we done it earlier, maybe halfway through, we probably would not have found much,’’ Ljungqvist said. ‘‘Now we have done some retests and we do have a few reports from the lab that are suspicious.’’

The IOC has declined to identify which athletes, sports or substances were flagged up, pending testing of the backup ‘‘B’’ samples.

If positive cases are confirmed, the IOC could retroactively disqualify athletes, nullify results and strip medals.

In 2004, the Athens Games produced a record 26 doping cases, more than double the previous Olympic high of 12 in Los Angeles in 1984. Six medalists, including two gold winners, were caught.

Ljungqvist took up Pound on his suggestion that the IOC medical commission formulate a policy on future retesting.

‘‘This is a good lesson,’’ Ljungqvist said. ‘‘We’ll follow your advice and together with WADA develop a strategy for further use of stored samples.’’

- AP