Here's a new twist on the drugs problem in cycling. US Customs and Border Protection (USCBP) officials have nabbed a couple of teenagers who were attempting to smuggle marijuana hidden inside the tyres of their bikes.

The teenage dope pedallers, a male and female aged 17, were detected by a USCBP sniffer dog at the border post in Douglas, Arizona.

Officials found about seven pounds of marijuana in the tyres of the couple's bikes.

Filling your tyres with plant material is a well-known emergency measure for mountain bikers stranded without a spare tube, but this form of grass is a bit pricy to use for that; the haul was worth an estimated $3,400 (£2,300).

Douglas sits in a valley at a shade over 4,000 feet above sea level, but officials did not reveal how high the smugglers got on their Mexican shopping trip.

Marijuana use in sport is controlled under the World Anti-doping Agency (WADA) code. In 2013 WADA raised the threshold for a positive test from 15 to 150 nanograms per milliliter, a level that would require an athlete to be a "pretty dedicated cannabis consumer" to test positive, Allen St. Pierre, executive director of the National Organization for the Reform of Marijuana Laws (NORML) told USA Today.