The list of players who have been suspended by Major League Baseball since 2005 for taking banned substances is 42 pages long, and it includes a passel of pharmacological quick fixes like boldenone, clenbuterol, formestane and stanozolol.

But recently, three players — major leaguers Daniel Stumpf of the Philadelphia Phillies and Chris Colabello of the Toronto Blue Jays and minor leaguer Kameron Loe — were suspended for taking Turinabol, an anabolic steroid straight out of a doping time machine.

The drug, whose chemical compound is dehydrochlormethyltestosterone, was widely used by athletes in East Germany. Developed in the 1960s by Jenapharm, an East German drug company, Turinabol became a foundation of the East German sports machine that rivaled the United States and the Soviet Union for medal supremacy at the Winter and Summer Olympics in the 1970s and 1980s.

But after the collapse of the Soviet bloc, Turinabol largely disappeared, and anti-doping experts do not know any major pharmaceutical company that produces the drug.

Yet athletes have found a way to get their hands on the drug, which can help muscles retain protein to build or repair them, and more player suspensions for the drug may be announced in the coming weeks, according to a person with knowledge of baseball’s anti-doping program.

Baseball, though, has only just started to catch players using Turinabol. Officials monitoring wrestling, weightlifting and other sports have been catching athletes using the drug in recent years. Last year, 11 of the 17 athletes suspended at the world weightlifting championships in Houston were found to have taken Turinabol, and they came from Azerbaijan, Belarus, Greece, Kazakhstan, Moldova and Russia.

“It is a relative epidemic, and this is not only North America,” said Dr. Christiane Ayotte, the director of the Montreal Doping Control Laboratory. “It might have started in the former Eastern bloc countries.”

Anti-doping experts believe unscrupulous chemists in the United States may be creating the drug or, more likely, it is being imported. Dr. Don Catlin, an anti-doping pioneer in the United States who ran the drug-testing lab at the 1984 Los Angeles Olympics, said Turinabol was easily obtainable online. He added that it was contained as a labeled ingredient in at least one supplement that can be bought off-the-shelf. It is also possible that the steroid is contained as an unlabeled product in a supplement, he said.

“I suspect somebody got a big supply of it somewhere and has been distributing it among friends and neighbors,” Catlin said. “One guy gets it and feels it’s working and tells all his buddies. Next thing you know, you’ve got a mini-epidemic.”

That Turinabol has shown up in supplements sold in America means some athletes may have unwittingly taken the drug. To be safe, Canadian authorities have warned their Olympic athletes to stay away from supplements sold in the United States, said Dr. Bob McCormack, the chief medical officer of the Canadian Olympic team.

“A high percentage of the raw materials for supplements come from China, where there is poor quality control, and there is a powerful lobby in the U.S. to combat oversight, so we tell athletes in Canada not to take U.S. supplements,” he said.

Although Turinabol proved infamously effective as an East German steroid, Catlin said, it does not clear the body quickly and is easily detectable. For years, it did not appear to be in widespread international use. An average of four to six positive tests were recorded annually by the 35 labs of the World Anti-Doping Agency, Catlin said. Then the number spiked to 73 in 2013, before lowering again to 17 in 2014 and 14 in 2015, he said, citing WADA statistics.

“These things come and go,” Catlin said. But he added, “To think just because it’s old means you can’t detect it is nonsense.”

In fact, one reason for the spike in suspensions is, like a cat-and-mouse game, anti-doping authorities have found more sophisticated ways of testing for the drug. In 2012, Tim Sobolevsky and Grigory Rodchenkov published a paper in the Journal of Steroid Biochemistry and Molecular Biology that outlined a more effective test for Turinabol.

Since then, anti-doping groups and sports leagues have updated their tests to better detect the drug. Turinabol had been on Major League Baseball’s banned list for years, but the league updated its testing techniques to look for the drug in 2014 as part of an annual review of its drug testing protocol.

Ayotte, the director of the Montreal Doping Control Laboratory, said the number of positive tests for Turinabol will start to drop as athletes realize that leagues and associations are doing a better job of looking for the drug.

But it will take time for word to get around. The baseball players recently caught using Turinabol may not have been aware of its East German provenance, Catlin said, or they didn’t care. “The side effects are horrendous, particularly to women,” he said. “But male baseball players probably don’t give a damn.”

Steven Ungerleider, the author of “Faust’s Gold,” a book about the East German doping system, said the emergence of Turinabol in baseball was “a little odd.”

“There’s a zillion other ways more sophisticated” to use banned substances and avoid detection, said Ungerleider, a sports psychologist in Eugene. “Why would anyone go back to using that? But people do crazy things.”