More than 360 guns were bought in Maryland last year by people barred from owning them because of a massive backlog in conducting gun transaction background checks, the Baltimore Sun reported.
The newspaper said last week that undercover troopers recovered nearly all of the 364 firearms sold to people who were ineligible to buy them, but four guns have not been retrieved.
"To us, the danger has not passed," state police spokesman Greg Shipley told the newspaper.
People with histories of mental illness or violent misdemeanor convictions, as well as felons and fugitives, were able to get and keep guns for three months or more before police reviewed the sales, The Sun said, citing records obtained under a Public Information Act request.
Would-be gun buyers in the state must pass a background check conducted by Maryland State Police. But a gun can still be sold without a background check if state troopers are unable to complete it within seven days and the dealer has no reason to believe the person purchasing the weapon is ineligible.
Dealers released 51,812 guns during the last year before a background check was completed, The Sun said.