If you ever watch video or look at pictures of the drug war in Mexico, you'll notice some pretty heavy weapons. This is a war being waged with rockets and plastic explosives, not pea shooters and Saturday Night Specials. Consider these incidents:

- A M26A2 fragmentation grenade used against a U.S. Consulate in Mexico in 2008

- Explosive projectiles and 21 grenades found during a raid in Guadalupe

- An unexploded grenade and pull ring used to attack a TV station in Monterrey

- Automatic weapons, including U.S.-made M16s, found at a cartel crime scene in May 2009

- U.S. military-issued ammunition found in a cartel raid in Reynosa in November 2008

You can't buy this stuff at a U.S. gun store. So where do the cartels get it? According to leaked diplomatic cables, there are three sources.

1. U.S. Defense Department shipments to Latin America, known and tracked by the U.S. State Department as "foreign military sales."

2. Weapons ordered by the Mexican government, tracked by the State Department as "direct commercial sales."

3. Aging, but plentiful arsenals of military weapon stores in Honduras, Guatemala and Nicaragua.

Even though these facts were well-known by the Obama administration, including Secretary of State Hillary Clinton and Attorney General Eric Holder, it blamed much of the violence in Mexico on U.S. gun stores.

"More than 90 percent of the guns recovered in Mexico come from the United States, many from gun shops that line our border," President Obama said in February 2009.

That was contested, but few listened to gun store owners and former vets like Lynn Kartchner, owner of Allsafe Security, a gun shop in Douglas, Ariz.

"We in the gun industry knew from Day One the allegations that the preponderance of sales came from gun stores like this one was totally not true," Kartchner said.

In fact, many of these weapons are getting to Mexico via the U.S. government. Tens of thousands of firearms and explosives are sold legally through the U.S. State Department to the Mexican government. These weapons are then funneled to the traffickers and cartels by corrupt officials within the Mexico Ministry of Defense and local and state police departments.

According to State Department documents, in 2009 Mexico bought nearly $177 million worth of American-made weapons, exceeding sales to Iraq and Afghanistan. That number includes $20 million in semi- and fully automatic weapons.

"Most of the M16s were sold legally to the Mexican government and disappeared," Kartchner added.

State Department cables obtained by WikiLeaks confirm that fear. One cable from November 2009 reads, "U.S. law enforcement has fair reason to worry a number of weapons simply disappear... "

Another from June 2009 says, "Rogue elements of the Guatemalan military are selling weapons to narcos."

“These are weapons that have been stockpiled either through U.S. aid programs or currently being shipped there under the guise of military support," said a confidential informant in Arizona who has worked for federal agencies such as the FBI, ATF and DEA.

"The governments and military in those countries realize that the economy is such that they are far better off to push these weapons north and sell them than they are to keep them in their own arsenals and reserves," he said.

Evidence of that is also contained in the Small Arms Survey. The table shows U.S. government sales of rifles, machine guns and handguns in the hundreds of thousands over a five-year period number.

And a GAO report from last year details both foreign military and direct commercial sales of arms from 2005 to 2009.

After looking at a warehouse full of high-powered weapons, allegedly stolen by a corrupt Mexican federal police officer, the informant said it was obvious to him that such weapons did not come from the "mom and pop" gun stores identified by the administration.