Schwazer served a doping ban of three years and nine months after testing positive for blood-booster EPO before the London 2012 Games.
He returned to competition in May and comfortably won the 50km event at the world race walking team championships in Rome, beating runner-up Tallent by three-and-a-half minutes.
Italy’s athletics federation confirmed overnight there had been “a notice of a violation”.
But it could not verify a report in Italian newspaper Gazzetta dello Sport that Schwazer’s positive was the result of a re-test of a January sample, taken after Schwazer had qualified for the Rio Olympics.
If true, Tallent stands to be promoted to first place in Rome.
The news comes less than a week after the Australian star was retrospectively presented with his Olympic gold medal for the 50km walk in London, where he crossed the line behind Russian drug cheat Sergey Kirdyapkin.
Schwazer has been on Tallent’s radar for a long time – the Italian also beat him to gold in Beijing 2008, setting an Olympic record in the process.
After May’s defeat in Rome, a bitter Tallent said the presence of the convicted drug cheat had caused him to lose focus.
He reiterated his concerns after his medal ceremony in Melbourne last Friday.
“Unfortunately, there is an Italian who was banned just before London who has just come back from a three-year and nine-month ban, and we have question marks over him,” Tallent said.
“He was the winner in Beijing and I was second behind him there.
“It then came out he was working with Lance Armstrong’s doctor, so there are question marks over him.
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