U.S. Sen. Kirsten Gillibrand announced Sundaythat she's backing a bill that aims to crack down on corrupt gun dealers as well as eliminate the flow of illegal guns into NewYork.

Almost 90 percent of the firearms used in New York City gun crimes come from out of state, and most of those guns are illegal, according to the Democratic senator, who plans to introduce the Gun Trafficking Prevention Act this week.

It comes on the heels of an undercover probe into gun shows by New York State Attorney General Eric Schneiderman. Investigators found an open marketplace for illegal weapons, with sellers disregarding mandatory background checks.

The probe also revealed a loophole in the law that holds the individual gun seller legally accountable but not the gun showoperator. The legislation would close the nation's "gun show loophole" and keep operators responsible.

"The Attorney General's critical investigation shows just how easy it is for guns to end up in the hands of dangerous people," Gillibrand said in a statement. "By cracking down on gun dealers who blatantly disobey the law as well as illegal gun traffickers and their vast criminal networks, we can reduce gun violence and keep our families and neighborhoods safe."

The undercover operation led to criminal charges against 10 New York gun dealers.

Schneiderman said the probe "confirmed what too many already know: In America, guns are freely available to all, regardless of criminal history or other prohibitive factors."

The new bill toughens penalties, making such sales a crime and suspending a dealer's license. Traffickers could face up to 20 years in prison. Kingpins who organize gun trafficking rings would be subject to an additional sentence of potentially five consecutive years in prison. And penalties could increase depending on the number of gunstrafficked.

In addition, individuals engaged in a conspiracy to traffic guns would be punished equally to those who actually traffic a gun. Corrupt dealers would be subject to a license suspension of up to six months and a fine of up to $2,500 per violation.