Authorities in Uruguay say the country's legal pot-growing clubs may be selling marijuana and cannabis products without approval, creating a kind of "gray market."

The pot-growing clubs are allowed to have 45 members who can collectively cultivate up to 99 plants for personal use, but they cannot sell the marijuana.

Uruguay became the first nation to approve marijuana legalization and regulation in 2013.

The law also allows Uruguayan adults to buy up to 40 grams of marijuana from pharmacies once a month. But there have been delays in implementing the pioneering plan.

National Drug Board chief Milton Roman said Thursday that the so-called "gray market" is not good for the marijuana legalization program and legal pot-growing clubs are being warned that violations of the law won't be tolerated.