Sen. Richard Blumenthal is demanding a crackdown on tiny devices known as "Glock switches" that turn semi-automatic handguns into fully automatic.

He says more of these devices are on the streets every day.

"Police know about them, and they're doing their best, but we need more focus on these tiny devices that can convert a semi-automatic weapon into an even more lethal automatic weapon, a machine gun-prohibited type firearm," Blumenthal urged.

The senator says he's pushing for more federal funds to help the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) and law enforcement agencies across the country fight the illegal modifications.

He says "Glock switches" have been popular among criminals who use it to turn legal guns into banned weapons for decades in the U.S.