The 37 year-old defeated Chudinov on February 20 to become five-time world champion in Oberhausen but now faces a two-year suspension if the findings are upheld.
A two-weight WBA title holder, Sturm reacted to being contacted with the news on Friday night.
“At first I was shocked. This is all very strange, especially that it took eight weeks until the came to light,” Sturm told the SID.
“I was certainly a hundred times tested in my career, with the blood and urine. There has never been anything and I have an absolutely clear conscience. I’m going to get a lawyer. I did not work 26 years for this. I always like to fight in the ring like a lion.”
Testing of the B sample has already been requested by Sturm and his team as the German begins the fight to clear his name.
Sturm’s case is the latest in a long line of high-profiles failures, the most recent of which were ex-European champions Erkan Teper and Igor Mikhalkin, plus heavyweight champion Lucas ‘Big Daddy’ Browne, veteran top division contender Antonio Tarver and former world title challenger Tony Thompson.