Dec. 6 (UPI) — U.S. Customs and Border Protection agents at the Laredo Port of Entry in Texas confiscated 21 pounds of testosterone and other steroids from a passenger vehicle and arrested a 25-year-old U.S. resident on Tuesday.

Agents said they found 4,760 pills and 201 vials of testosterone and other steroids in the vehicle after it was stopped by agents for an enhanced search with canines at the Juarez-Lincoln Bridge.

Anabolic steroids are Schedule III substances under the Control Substance Act, with only a small amount approved for legal use by humans and veterinarians.

“Our frontline CBP officers maintain strict vigilance and their application of inspection experience and technology led to the discovery of a significant amount of steroids deeply hidden within a vehicle,” Port Director Alberto Flores, Laredo Port of Entry, said in a statement.

“It’s unusual to encounter steroids in large quantities such as this case and this seizure underscores the commitment of CBP to ensure the security of our border and stem the commercialization and abuse of such controlled substances.”

Along with seizing the drugs and arresting the female driver, who was not identified, CBP agents took possession of the 2012 GMC Terrain she was driving as part of their investigation.

“Case studies and scientific research indicate that high doses of anabolic steroids may cause mood and behavior effects,” CBP said in a statement. “In some individuals, anabolic steroids can cause dramatic mood swings, increased feelings of hostility, impaired judgment and increased levels of aggression, often referred to as “road rage.”