Paulina Rubio performing at The Pearl Theatre In Palms Hotel and Casino. Las Vegas, Nevada - 29.06.07

The 36-year-old and her husband Nicolas Vallejo-Nagera are alleged to have travelled to the U.S. consulate in Juarez, Mexico, in September (07) to apply for their visa, and both underwent a medical exam at the International Medical Clinic as part of the process.

But the couple's tests came back positive for marijuana use, while Vallejo-Nagera's also showed results for ecstasy and cocaine, reports Mexican newspaper El Diario de Chihuahua.

Rubio's spokesperson has denied all knowledge of the incident, telling Peopleenespanol.com, "We find out about things from the media. We don't know anything because this supposedly occurred in Mexico. But lawyers are already working on it in Mexico. We really don't know anything."

Source: WENN