Nearly half of the guns that crossed state lines and were used in crimes in 2009 were sold in just 10 states

Nearly half of the guns that crossed state lines and were used in crimes in 2009 were sold in just 10 states, according to a report being released Monday by a mayors' group.

Those states accounted for nearly 21,000 guns connected to crimes in other states, said the survey by Mayors Against Illegal Guns, an association of more than 500 mayors led by New York's Michael Bloomberg and Boston's Thomas Menino.

The Bureau of Alcohol, Tobacco, Firearms and Explosives traced more than 145,000 guns used in crimes in 2009 and found that more than 43,000 of those weapons were sold in other states.

Forty-nine percent of those guns were sold in Georgia, Florida, Virginia, Texas, Indiana, Ohio, Pennsylvania, North Carolina, California or Arizona.

States were also ranked by the number of crime guns exported per 100,000 inhabitants. Mississippi led that list, followed by West Virginia, Kentucky, Alaska, Alabama, South Carolina, Virginia, Indiana, Nevada and Georgia.

Those states, the report said, have more relaxed gun laws, suggesting that "criminals and gun traffickers may favor certain states as the sources of guns."

For example, in states that do not require background checks for handgun sales at gun shows, the crime-gun export rate was two-and-a-half times as much as the rate in states that do require such checks.