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Prosecutors say they confiscated 1,300 knives in an undercover investigation.

Many of the knives were purchased from national retailers like Home Depot, Paragon Sports and Eastern Mountain Sports.

He says the sale of everything from switchblades to so-called gravity knives which have side folding blades must stop.

Officials say the seven companies are cooperating with the crackdown.

"First, these companies have agreed to cease and desist the sale of these knives in New York State, forever. Second, they have agreed to turnover the stocks of their illegal knives, part of which are on this table here today -- more than 1,300 knives. Finally, they have agreed to relinquish the profits made from the sale of these illegal knives over the past four years -- two years beyond the criminal statute of limitations which will be largely split between the city, the state and district attorneys office who wish to partner with us in the fight against illegal knives," Vance Jr. said.

DA Vance says in exchange for their cooperation, the companies will not face charges.

They have agreed to pay the state and city a total of nearly $2 million in profits from previous sales.

Officials say one-third of the homicides in Manhattan over the past year were committed with an illegal knife.

Vance Jr. says a second phase of the investigation is already underway and will target out of state vendors selling illegal knives to New York residents.