The 23-year-old, who won the silver medal at the European indoor championship in Prague and finished fourth at the world championships in Beijing last year, failed an out-of-competition drug test on Feb. 6, her manager Venitsa Atanasova said.
Atanasova, however, said that Petrova, who also won the European U-23 title in 2013, took this medication only at the end of last year.
"Once it was announced in October that medicines containing meldonium are prohibited from Jan. 1, 2016, she stopped using it," Atanasova said.
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Meldonium was added to the World Anti-Doping Agency's list of banned substances on Jan. 1. Since then, more than 100 athletes have been found to have used meldonium.
"Gabriela has not been charged with anything, she's not banned," Atanasova said. "We were only informed about the positive sample."
Atanasova said that Petrova, who was named Bulgaria's Athlete of the Year in December, remains hopeful that she will compete at the Rio 2016 Olympic Games.
"We don't worry about Rio," she said. "We worry about her image. She's not accused of anything but it's so stressful."
Use of meldonium was widespread before the ban. One study showed 490 athletes who competed in last year's European Games in Baku had taken it.
Grindeks, the Latvian company that is the main supplier of the drug, says it could protect athletes from cell damage but was unlikely to improve their performance.
(Reporting by Angel Krasimirov; Editing by Digby Lidstone)
