Authorities say more homemade guns — sometimes called “ghost guns” because they can’t be traced — have shown up at crime scenes in recent years. The West Coast has the lion’s share of ghost gun crime.

“We’ve had very few of these recovered in our four-and-a-half states that have been associated with a criminal act,” said John Ham, spokesman for the Bureau of Alcohol, Tobacco, Firearms and Explosives’ Kansas City field division, which covers Iowa, Missouri, Kansas, Nebraska and southern of Illinois.

He said ATF officials are tracking the issue, even if they can’t track the history of the individual guns.