MEXICO CITY — Mexico’s Congress called on the United States to tighten gun-control laws after 20 elementary school students were shot dead in Connecticut, saying drug cartels fill their arsenals with weapons bought north of the border.

The Permanent Committee of the Congress sent its statement in an email Thursday after former President Felipe Calderon wrote on his Twitter account this month that the end of the U.S. assault-weapon ban in 2004 is one of the causes of violence in the region.

A 2009 analysis of Justice Department data by the Government Accountability Office (GAO) found the number of firearms seized in Mexico that could be traced to the United States more than doubled to 6,700 in 2008 from 3,090 in 2004.

The same GAO report found that the number of high-caliber, high-powered weapons in Mexico was rising, and that the United States lacked a comprehensive strategy to prevent arms trafficking to Mexico.

The “freedoms” of the U.S. weapons industry are destroying Mexico and the United States, said Ricardo Mejia Berdeja, a Mexican lower house lawmaker, according to Congress’ statement.

“If we don’t stop the trafficking of weapons we won’t win the battle against organized crime,” he said.

President Barack Obama said he’s looking for ways to curb gun violence after the Dec. 14 shooting in Newtown, Conn., while Sen.  Dianne Feinstein, a California Democrat, has said she’ll introduce a bill to reinstate a ban on assault weapons.