The paper said the Commonwealth Games organisers had sent a report to Sri Lanka's National Olympic Committee and informed the boxer of the result with his urine "A" sample.
There was no immediate confirmation from the committee or Sri Lanka's sports authorities.
Wanniarachchi had beaten Welshman Sean McGoldrick in the final round of the Bantamweight category to clinch the gold.
The boxer can request a "B" sample test. If the outcome remains unchanged, he risks being stripped of his gold medal and could face a two-year ban from all competition.Sri Lanka also won one silver and one bronze medal for boxing and weightlifting during the October 3-14 Delhi games.