More than 68,000 illegally trafficked guns in the U.S. over five years came from unlicensed dealers who do not require background checks, according to new data released Thursday by the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Justice Department officials said this accounted for 54% of illegal firearms trafficking in the United States between 2017 and 2021. ATF Director Steve Dettelbach said the guns were used in 368 shootings, which are more difficult to investigate because unlicensed dealers are not required to keep records of their sales so federal agents can track them to the original buyer of the weapon.

The report, ordered by Attorney General Merrick Garland, is the first in-depth analysis of a gun trafficking investigation in more than 20 years. It reviewed more than 9,700 closed ATF firearms trafficking investigations opened between 2017 and 2021. Firearms trafficking is the intentional transfer of firearms to illegal markets for criminal purposes or possession.

The second largest percentage of gun trafficking cases investigated by the ATF are straw purchases, in which someone buys a gun for someone who cannot legally obtain a gun themselves.

The report also shows that in cases where investigators were able to ascertain the recipient’s background, nearly 60 percent of the recipients of smuggled firearms had been convicted of a felony. In addition, Detelbach said that in nearly 25 percent of cases, trafficked guns were used to commit other crimes. That included more than 260 murders and more than 220 attempted murders, the report said.

“So the data shows that those who illegally traffic guns, whether out of trunks, at gun shows or online, are responsible for the real violence in this country,” Dettlebach said. “Simply put, In other words, you cannot illegally aid armed violence without being responsible for the violence that ensues.”

The report found that the average number of firearms trafficked per case was 16. People who purchased firearms through unlicensed dealers purchased an average of 20 weapons, while those who purchased through straw purchased an average of 11 firearms, the report said.

The Biden administration has separately proposed a rule that would require thousands of gun sellers to be licensed and undergo background checks. The Justice Department said the bill targeted sellers in the business of selling guns, but the proposal quickly drew protests from gun rights groups who argued it could defraud ordinary people who sometimes sell their own guns.

The rule, which has not yet been finalized, is expected to affect between 24,500 and 328,000 sellers. During the five years documented in the report, the ATF investigated 3,400 unlicensed dealers.