Positive findings for "trace amounts of a fertility drug" led to welterweight Benn's much-hyped catchweight fight in London with compatriot Chris Eubank Jr being called off in October.
The WBC said in a statement that Benn's team had this month provided a detailed breakdown of his diet and consumption of supplements.
It found no conclusive evidence that Benn intentionally ingested the banned substance Clomiphene and no procedural failures.
"Benn’s documented and highly-elevated consumption of eggs during the times relevant to the sample collection, raised a reasonable explanation for the Adverse Finding," the WBC said.
"The WBC Nutrition Committee will work with Mr. Benn’s team to design a nutrition program geared to avoid the risk of a future adverse finding caused by nutritional factors."
The WBC said it would also raise its concern about Clomiphene as a food contaminant and the potential of false positives with world anti-doping agency WADA.
Benn remains under investigation by UKAD, Britain's anti-doping body.
The Briton, whose father Nigel was a super-middleweight world champion, relinquished his licence with the British Boxing Board of Control after the Eubank fight was called off.
