NEW YORK -- Officials say a New York City undercover investigation at an Arizona gun show found that private sellers didn't always require background checks of buyers.
Mayor Michael Bloomberg's sting operation came weeks after a Tucson shooting that killed six people and injured 13 others.
Officials told The New York Times that undercover investigators were able to buy guns even after telling sellers they probably couldn't pass background checks.
Bloomberg is scheduled to show an undercover video on Monday of illegal firearms sales at the Phoenix gun show last week.
The sting was part of the Bloomberg administration's effort to crack down on illegal gun sales nationwide.
Bloomberg last week urged Congress to make sure the system for background checks on firearms purchases includes the names of everyone prohibited from buying weapons.