An experimental performance-enhancing drug is available online, before it has been approved for human consumption, The New York Times reports. Two cyclists recently tested positive for the drug, FG-4592.

The drug, taken as a pill, increases production of red blood cells. An increase in oxygen-carrying red blood cells can help make athletes faster and improve their endurance. Athletes can order FG-4592 from chemical-supply companies online, the article notes. The companies selling the drug say it is meant only for researchers, and are not marketing it to athletes.

“What’s amazing to me is that it is out there for sale on the Internet,” said Don Catlin, a consultant on drug testing and former director of the UCLA lab that performs drug tests for the Olympics.

The two cyclists accused of taking FG-4592 are awaiting results of a backup test. Fabio Taborre of Italy was provisionally suspended this week after testing positive. Carlos Oyarzun of Chile was expelled from this month’s Pan American Games after receiving positive test results. He has denied taking the drug.

FG-4592 is in a class of substances prohibited by the World Anti-Doping Agency. More than 600 sports organizations use the agency’s lists in deciding which substances to ban.

At least three chemical-supply companies sell FG-4592, even though it is theoretically only available to participants in clinical trials conducted by AstraZeneca and FibroGen. In order to purchase the drug, a person needs something in writing saying they will use it for research purposes, according to Jane Lee, a technical-support specialist at Selleck, a company that sells the compound. FG-4592 must be sent to a university or research facility.