After a meeting in Bangkok of its ruling Bureau, FINA said it would examine samples to check for the presence of "plasticizers" - tiny particles of plastic left over from blood bags.

In September, FINA said of the 391 tests taken Championships, held between July 15 and August 2, none came back positive.

A total of 162 samples were screened for the blood-boosting hormone Erythropoietin (EPO).

The Championships were overshadowed by controversy because of the row over the high-tech swimsuits worn by several competitors and which led to Michael Phelps, who won five gold medals in Rome, to threaten to quit the sport unless the rules were modified.

The suits were subsequently banned.

FINA also says it will look into the introduction of a "biological passport" programme to monitor swimmers' blood profiles for evidence of doping.

FINA will also consider storing drug samples for at least eight years after World Championships for possible future retests, they said.