Vending machines distributing the drug marijuana are to begin operating in the US state of California.

The machines can only be used by people who have been prescribed the drug for health reasons.

Patients will have to provide a prescription, and be fingerprinted and photographed before being allowed to use the facilities.

Eleven US states allow the medicinal use of marijuana, primarily for pain relief, but it remains controversial.

Vince Mehdizadeh, owner of the Herbal Nutrition Centre in Los Angeles, where one of the two first machines is based, said it would allow patients to buy extra supplies whenever needed.

Series of checks

Once the users have been photographed, fingerprinted and have shown their prescription, they will be issued with a card which can be used in the machines, he told KWTX News 10 in the US.

"They'll be greeted by a security guard right there. They'll slide the card in and they'll fingerprint in to verify that it's them," he was quoted by KWTX News 10 as saying.

"A camera takes a picture of them, verifying that they're actually at the machine. And they get the medicine and they move on."

The operators think that vending machines issuing prescription drugs could become a common sight in the US.

Proponents say marijauna is a valuable tool for relieving pain and stimulating appetite in the sick.

However, it remains banned by the 1970 Controlled Substances Act and the US federal government does not currently recognise any legitimate medical use.