The sources said the doping violation occurred at the Jamaica International Invitational meeting on May 4 in Kingston.
Jamaica Athletics Administration Association (JAAA) president Warren Blake told Reuters on Saturday an athlete had tested positive at the meeting but declined to give a name.
"What I can confirm is in fact that we do have an adverse analytical finding coming out of the May Invitational meet," he said.
"But so far to date, and that is until this morning, we have not as an association been informed of the result of the B sample testing.
"As such I'm not able to speak to the name of the athlete or to say anything that may identify which athlete it is," he added.
Neither Campbell-Brown nor her manager could be reached for comment.
Campbell-Brown is Jamaica's most successful female athlete and the biggest name in track and field to fall foul of the drug testers since disgraced American sprinter Marion Jones.
Jones served a six-month prison sentence and was stripped of the five medals, including three golds, she won at the 2000 Sydney Olympics after admitting to using performance-enhancing drugs.
Local media reports said Campbell-Brown had been present at the laboratory in Canada when her B sample was tested earlier this week.
The finding comes after Jamaican 400 metres runner Dominique Blake received a six-year ban on Thursday for her second doping violation since 2006.
Diuretics, which promote the production of urine and treat medical conditions including high blood pressure, are viewed as masking agents by the World Anti-Doping Agency (WADA).
The penalty for a positive result ranges from a public warning to a two-year suspension depending on the circumstances.
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