(Reuters) - The International Olympic Committee (IOC) is retesting five doping samples from the 2004 Athens Olympics after an adverse finding in the A sample, an official said on Monday.

"There are adverse analytical findings in five cases," the official told Reuters.

The official told Reuters the B samples were yet to be tested. He gave no details of the sports or athletes involved.

The IOC has been retesting samples from past Games to detect offenders with methods of detection that did not exist at the time. Samples are frozen for eight years.

Several positive cases were discovered after retesting for samples at the 2008 Beijing Games

(Reporting by Karolos Grohmann; Editing by John Mehaffey)