The Arizona Department of Health Services could revoke more than a dozen medical-marijuana cards, saying patients and caregivers have either violated the state's new medical-marijuana law since receiving a card or lied about their histories when applying for one.

Health officials on Tuesday said they have revoked the cards of two patients, but because of a confidentiality clause in the law, they could not say specifically why the cards were taken away.

Typically, they said, cards are revoked if a law-enforcement agency notifies health officials of an arrest tied to buying or selling medical marijuana, which is illegal. The law does not allow the sale of marijuana to patients outside of dispensaries, which have not yet opened in Arizona. Instead, patients can only give marijuana to each other, receiving nothing of value in return. Or, health officials said, cards can be revoked if patients fail to properly secure plants in a locked facility.

Health officials have revoked the medical-marijuana cards of two caregivers and are reviewing the histories of 10 others. Caregivers typically grow marijuana for themselves and other patients, too.

Tom Salow, a rules administrator for ADHS, said all those caregivers could soon lose their marijuana cards, too, because they either did not disclose a violent-crime history on their applications or they have violated certain drug laws.

He said the agency has fallen behind in revoking the cards because officials must research applicants' backgrounds and issue the cards in a short time.

"(The law) doesn't give us enough time to get background checks from the Department of Public Safety and make a decision on the application in enough time," Salow said. "We approve the applications, give them a card, and if it comes back with a hit after research ... and a decision to revoke is made, then we revoke. It takes us a little while -- it isn't as easy as we thought it would be."

ADHS Director Will Humble said the agency expects to catch up soon on the backlog and process future cases more quickly with the imminent hiring of outside attorneys.

Those lawyers, paid for with fees generated from the medical-marijuana program, will help health officials more quickly decide whether revocations meet legal standards, he said.

Voters in 2010 passed a measure to allow people with certain debilitating medical conditions, including chronic pain, cancer and muscle spasms, to use medical marijuana.

They must receive a recommendation from a licensed physician and register with the state, which issues ID cards.