When it comes to using performance-enhancing drugs, athletes rarely act alone. A new investigative report has accused Nike running coach Alberto Salazar of facilitating his protégés using testosterone, as well as prescription asthma and thyroid medications.

Athletes and coaches who have worked with Salazar and his group, the Nike Oregon Project (NOP), made the claims in an article on ProPublica and an hour-long BBC program called Catch Me If You Can. Although none of Salazar’s athletes have tested positive for illegal substances, they suggested that this was due to his knowledge of how to work the system.

Former assistant Nike Oregon Project coach Steve Magness provided photo evidence that his top protégé, Galen Rupp, was on prednisone and testosterone at the age of 16 in 2002. Prednisone, used to treat asthma, is banned during competition, but Rupp received a therapeutic use exemption (TUE) after claiming he suffered from it since childhood. The doctor who diagnosed him, Dr. Loren Myhre, was employed by Nike. Prednisone also isn’t banned in any form during out-of-competition periods, so Rupp could have theoretically used it without a TUE until a week before competitions.

However, using testosterone as a supplement is always forbidden. Magness claimed that Salazar used his son, an employee with Nike, as a guinea pig to find out which testosterone would show up on tests. Former NOP massage therapist John Stiner also told the BBC that Salazar asked him for a tube of Androgel, a testosterone cream, while two-time Olympian Kara Goucher said that Salazar encouraged her to take unprescribed thyroid medication to help lose weight after giving birth.

Rupp and Salazar have denied all the allegations against them. Salazar also said in a statement that those who spoke out used “false assumptions and half-truths in an attempt to further their personal agenda ... I believe in a clean sport and a methodical, dedicated approach to training.”

Nike released its own statement on the BBC documentary, declaring that “we take the allegations very seriously as Nike does not condone the use of performance-enhancing drugs in any manner.”