Washington (CNN) Hong Kong's police have routinely used tear gas in their attempts to dispel pro-democracy protests that have roiled Hong Kong for weeks -- and it turns out the tear-inducing, throat-choking crowd control devices may have been made in the USA.

In recent years, the US government has authorized millions of dollars' worth of military and defense equipment exports to the government of Hong Kong, equipment that includes "toxicological agents" such as "tear gases and riot control agents."

But as protesters continue to roil Hong Kong with their demands for greater freedoms and China begins to mass troops at the border, lawmakers on both sides of the aisle are raising concerns about the role the US could be playing in abetting any violent suppression.

Republicans and Democrats in Congress have issued statements calling for the US to block those exports in the future -- and some are planning to introduce legislation to stop more sales.

Bipartisan concern

"USA banned exporting tear gas crime control equipment to China after the Communist Party massacred dissidents in Tiananmen Square. If Xi Jinping doesn't stop eroding Hong Kong's sovereignty & halt attacks on protestors, the US must consider applying the same policy to Hong Kong," Republican Sen. Ted Cruz of Texas wrote on Twitter last month.

Rep. Jim McGovern, a Massachusetts Democrat, took to Twitter on Monday to raise concerns as well.

"Due to the excessive use of force & lack of restraint by #HongKong authorities, I will soon introduce legislation to suspend U.S. sales of munitions, police & crowd control equipment to the #HongKong police," he wrote.

The Department of State did not respond to a request for comment.

The Department of Commerce said in a statement that it uses export licenses to regulate "the export of crime control items for the protection of human rights around the world. In particular, US exports of tear gas and other law enforcement equipment, such as pepper spray and police helmets, shields, batons, to Hong Kong require a license from the Department, and the Department consults with the Departments of State and Defense in reviewing such license applications. When licenses are issued, the Department remains committed to strictly enforcing those licenses."

The responsibility for granting licenses for the export of tear gas was moved to the Department of Commerce in 2016, after tear gas was no longer classified as military weaponry on the State Department's US Munitions List.

Firearms and ground vehicles

In 2017, the first year of the Trump administration, the US government authorized more than 600,000 items for export to Hong Kong's government, equipment valued at more than $1.9 million, according to a State Department report that tracks the export of military and defense articles to foreign governments and international organizations.

In addition to $81,000 worth of toxicological agents -- which can include tear gas -- the exports included 291 "non-automatic and semi-automatic firearms" and 20 ground vehicles.

It is not clear whether those firearms and ammunition included nonlethal guns and rubber bullets or bean bag rounds like those that have been used against the protesters in recent days.

Ever since the Chinese Communist Party's violent 1989 crackdown on pro-democracy protesters in Tiananmen Square, the US government has banned such weapons exports to mainland China but has authorized exporting military gear to Hong Kong's government for years, dating back to when it was a British colony.

"The Hong Kong Special Administrative Region and the People's Republic of China are treated as two separate destinations under US law for export control purposes," according to the Commerce Department's Bureau of Industry and Security.

In 1999, just two years after the UK handed over Hong Kong to China, the US authorized the export of chemical agents and chemical agent-dispersing equipment to Hong Kong's government, in addition to handguns and other military gear.

In 2015 and 2016, the Obama administration similarly approved $177,000 worth of toxicological agent exports to Hong Kong, as well as 333 "non-automatic and semi-automatic firearms."