Mexican runner Yamile Herrera is being provisionally suspended for the use of performance enhancers. After a stellar performance at the World Relays in Botswana, the stage seemed set for Mexico. Their four-star studded sprinters had finally broken the Latin American record. Among the four, Herrera, 26, was the oldest, and despite a sixth-place finish, the quartet was lauded. However, everything has come crashing down after the sprinter was provisionally banned by the AIU.

The Athletics Integrity Unit (AIU) announced that it had provisionally suspended the Mexican for using a banned substance.

“The AIU has provisionally suspended Yamile Herrera (Mexico) for Presence/Use of a Prohibited Substance (Oxandrolone),” reads the AIU’s statement on X. No further details have been provided regarding Herrera’s suspension.

Oxandrolone is a synthetic anabolic steroid that is part of the AIU’s banned substance list. That’s because it mimics the hormone testosterone, which promotes muscle growth and more. That allows an athlete to recover rapidly and perform at a higher level.

The news comes as a shock to the Mexican racing community, as it could mean their result at the World Relays is disqualified. Officials have not confirmed the matter, but Herrera has not raced since May 6th, when she was notably absent from the National First Division Championship roster.

Her last race was the RunTime Performance Tour Fecha 6 in Ciudad de Mexico. She did relatively well at the event, finishing first in both the 100m and 200m. This winning streak has defined her 2026 season, a sharp reversal from 2025, when her results were significantly worse.

That especially included the Mexican Championships, where she finished fifth in both the 100m and 200m finals. In fact, Herrera clocked 23.81 seconds in the 200m, finishing well behind winner Miriam Sanchez (22.60), Cecilia Tamayo-Garza (22.97), and Alejandra Paulina Ortiz Hernandez (23.55). The same happened in her 100m race, as she registered 11.70 for fifth behind the same trio who clocked 11.18, 11.35, and 11.54 respectively.

But since the turn of the year, the 26-year-old has improved her times and performances. That improvement has come slowly but steadily as she recently clocked personal bests. Herrera registered 11.55 (+1.7) in April 2026 for a personal best in the 100m during the Encuentro de Relevos Pista y Campo Prof. She then clocked 23.60 seconds one day later in the 200m at the same event in Mexico.

Both races marked personal bests in her buildup to the 2026 World Relays. There, alongside Brandon Heredia, Gerardo Lomeli Ponce, and Alejandra Urias, the Mexican team thrived.

Herrera and company set a national record at the 2026 World Relays.

Few anticipated much from Mexico at the 2026 World Relays in Botswana. They certainly picked their best team, including Brandon Heredia, Gerardo Lomeli Ponce, and Alejandra Urias. Urias was the reigning Mexican U20 national champion in both the 100 and 200m, while Heredia was a five-time national champion. That included the 2025 season, where he finished first in the 4x100m relays and third in the 100m sprint.

Ponce, on the other hand, was also a reigning national champion in both the 100m and 200m. Furthermore, Yamile Herrera was also selected, with the 26-year-old recently putting up some of her best times in the 100 and 200m. Still, the world-class teams from Jamaica, Australia, and Great Britain meant that expectations were low.

The quartet proceeded to disrupt expectations. They made it through into Qualifying Round 2, and there the quartet clocked a stunning 41.57 in the mixed 4x100m relays. It set a new national record in the discipline and made them the best relay team in Latin America.

Questions have been asked whether the record will stand in light of Herrera’s provisional suspension. The 26-year-old will have to defend herself and appeal the decision, although Herrera has not yet made a statement on the matter.

For now, the record-breaking relay performance that put Mexico on the map remains in limbo. The AIU’s process will likely determine whether that achievement stands or falls. For now, however, the focus has shifted from one of the country’s most promising sprinting stories to questions that could reshape everything.