Gun shows have been a major target of criticism by firearm opponents, mostly because sales are between private parties and don’t always require background checks, depending upon the state in which they are held.

Some studies and investigations have found these shows are the source of guns disproportionately used in crimes.

The two-week period after Nevada gun shows—among the least restrictive in the country—brings a 70-percent spike in gun violence in the areas within a drive across the border in California, according to the latest study by a team of scientists from the University of California–Berkeley.

The increase in death and injuries from firearms happened within the radius of a two-hour’s drive from the Nevada gun shows in the two weeks after they were held, the doctors report in the journal Annals of Internal Medicine.

The rate per 100,000 people increased from 0.67 to 1.14, they write. That translates to roughly 30 more deaths or injuries than the control, two weeks before the gun shows, they write.

“Results from this study suggest that California gun shows are not associated with short-term increases in firearm injuries but that Nevada shows are associated with cross-border increases in firearm injuries in California,” they conclude.

California requires background checks at gun shows. Nevada does not require such checks.

The assessment included 915 gun shows between 2005 and 2013 (640 in California and 275 in Nevada). The shows were located using lists published in the “Big Show Journal.”

The injury data was compiled with death records from the California Department of Public Health Vital Records, as well as hospitalization records from the Office of Statewide Health Planning and Development (California coding of such injuries in mandatory, according to the authors).

But there were limitations, the authors concede. For instance, Nevada gun injuries and deaths were not statistically assessed. Also, the firearms for the catalogued California deaths and injuries were not categorized, or tied in any way to the Nevada shows. And most importantly, perhaps, contextually few firearm injuries occurred in the regions exposed to Nevada gun shows, they write.

One of the limitations was previously identified in a publication by one of the current authors. Garen J. Wintemute, an emergency medicine physician at UC Davis Medical Center, co-wrote a study in 2010 in the American Journal of Public Health that blasted previous studies linking gun shows and gun violence as “fatally flawed.” That paper was cited in this current paper, as well.

But some of the scientists involved maintain that California’s gun restrictions could be curbing firearm assaults in the Golden State.

“Our study suggests that California’s strict regulations—on firearms, generally, and on gun shows, specifically—may be effective in preventing short-term increases in firearms deaths and injuries following gun shows,” said Ellicott Matthay, a doctoral student at UC Berkeley, in a school statement.