Schwazer, who was suspended for three years and nine months after admitting he used the blood booster erythropoietin (EPO) in 2012, now faces a life ban from the sport.
The athlete, who won the world 50km title in Rome this year, tested positive in May for a steroid that he said he had not knowingly taken.
The repeat analysis has also proved to be positive, Schwazer's lawyer told the Italian news agency ANSA, adding that he had been banned by the International Association of Athletics Federations (IAAF).
Gerhard Brandstaetter said he would appeal against the suspension immediately, adding that his client's urine sample must have been tampered with.
However, the July 18 deadline for Olympic entry gives Schwazer very little time to get into next month's Rio Games.
His trainer, Sandro Donati, said the walker was the victim of "sporting homicide" by the IAAF.
Before Schwazer's 2012 ban and exclusion from that year's London Games, he was a hero in Italy for winning Olympic gold, having beaten a 20-year record set by Russian Vyacheslav Ivanenko by more than a minute.
(Reporting by Gavin Jones; Editing by Tony Jimenez)
