As members of Congress scrutinize a firearm accessory found at the scene of the Las Vegas massacre, North Dakota’s senators said they wanted to learn more about the devices Wednesday.

A “bump stock” is a legal accessory that uses a gun’s recoil to accelerate its rate of fire. They were found on at least a dozen of the 23 firearms discovered in the wake of Sunday’s shooting that killed 58 people and injured hundreds more, according to the Washington Post.

More than two dozen Democratic senators, led by California’s Dianne Feinstein, introduced legislation Wednesday to ban bump stocks, trigger cranks and other accessories that speed up a semi-automatic rifle’s rate of fire, according a news release. It includes exceptions for law enforcement and the government.

Feinstein called the accessories a “loophole” in the heavy restrictions on automatic weapons, which fire bullets much more rapidly than semi-automatic ones.

“The only reason to fire so many rounds so fast is to kill large numbers of people,” she said in a statement. “No one should be able to easily and cheaply modify legal weapons into what are essentially machine guns.”

Both of Minnesota’s senators, Democrats Al Franken and Amy Klobuchar, are cosponsors of the bill. Some congressional Republicans have said the devices warrant scrutiny, according to the Post.

Sen. Heidi Heitkamp, D-N.D., is not a cosponsor of the bill and a statement issued by her office didn’t say whether she would support a ban.

“I haven’t heard much about bump stocks before, and I first want to learn more about them,” she said.

Sen. John Hoeven, R-N.D., called for gathering all of the facts about what happened in Las Vegas.

“I am not familiar with bump stocks, but we need to look into them as part of getting all of the information on this tragic event,” he said in an emailed statement.

Rep. Kevin Cramer, R-N.D., didn’t return a call seeking comment by 5 p.m. Wednesday.

Cody Schuh, owner of the Bismarck gun shop Shooter’s, said they sold out of bump stocks after Sunday’s shooting. He said that likely has to do with fears the devices would be banned or otherwise regulated.

“My distributors are all out too,” Schuh said.

Schuh said the bump stocks are a “novelty device that, within practice, doesn’t usually work that well” and typically cost between $159 and $299. He doubted banning them would have much effect and said the focus should be placed on mental health issues that would prompt somebody to carry out a mass killing.

“You could try and regulate the stock all you want, but the market will produce something else to go around it,” Schuh said.