Major League Baseball officials will conduct an investigation to determine if any links exist in the cases of four players who tested positive for the banned steroid stanozolol, Commissioner Rob Manfred confirmed Monday. New York Mets pitcher Jenrry Mejia, Minnesota Twins' Ervin Santana, Seattle Mariners pitcher David Rollins and Atlanta Braves pitcher Arodys Vizcaino were each suspended for use of stanozolol, an easily detected substance that has popped up on baseball drug tests for decades.

“Other than the similarity of substance, I have no reason to believe right now that they’re connected,” Manfred told the Associated Press. “Having said this, whenever we have a series of tests for a single substance, we undertake an investigative effort to determine whether there’s a connection and what that connection might be.”

Stanozolol, better known as Winstrol in its pill form, is an anabolic steroid used by athletes as a performance-enhancing substance since the 1960s. It’s most popular with weightlifters due to its ability to facilitate weight loss without a reduction in muscle mass, though it’s also appeared on track-and-field and baseball circles. Canadian track star Ben Johnson lost a gold medal after he tested positive for the steroid at the 1988 Summer Olympics, the New York Times reported.

Baseball officials are well aware of stanozolol, which shows up on any standard urine test for performance-enhancing drugs and cannot be hidden by masking agents. Former Baltimore Orioles slugger Rafael Palmeiro tested positive for the steroid in 2005. The steroid is so commonly known that experts consider it laughable for a player to expect to avoid detection.

“The question is how do they think they can take stanozolol and not test positive? You can beat a test much easier with fast-acting testosterone. No one who knows they’re going to be tested these days should knowingly take this,” Victor Conte, founder of now-shuttered steroid distributor BALCO, told the New York Daily News.   

Mejia and Santana each said they would never knowingly ingest a banned substance. Manfred did not deny that possibility and said the league has not yet found any evidence of a connection between the failed tests, as was the case in 2013, when 14 MLB players were suspended for obtaining performance-enhancing drugs from the now-closed Biogenesis Clinic in Florida.

“The thing you need to remember is that the players might not be aware of the exact substance they are using,” Manfred told the New York Times. “I’m sure they knew it was a performance-enhancing substance, but whether they knew it was testosterone or stanozolol, I don’t know. The possibility I’m raising is that they are getting advice from someone, and it’s bad advice.”