GUATEMALA CITY (Reuters) - Guatemala is investigating radio advertisements seeking elite ex-soldiers, who have been known to work for drug cartels, to smuggle goods into Mexico, officials said on Thursday.

A Kaibil sniper is seen with full gear during an exhibition in the Special Forces Brigade, known as "Kaibil's Hell", in Poptun, Peten, October 30, 2006. A REUTERS/Carlos Duarte

The ads were broadcast in the lawless northern jungle region of Peten, home to a tough military training center for Kaibil soldiers, infamous during Guatemala’s civil war as a brutal guerilla-fighting, special forces unit.

“We invite all citizens who have served in the military and graduated as Kaibils to work securing vehicles transporting merchandise to Mexico,” the radio spot said, according to a local newspaper. The ad gave a telephone contact number.

Former Kaibil soldiers have been lured to work as assassins and run security for powerful drug lords by cash payments that can be as much as 10 times the average army salary, according to a Kaibil commander interviewed by Reuters.

Spokesmen for the Interior Ministry and the army said authorities still were investigating the origin of the radio ads, which may have been transmitted on pirated airwaves.

Created in the 1970s to fight a counter-insurgency campaign against leftist guerrillas during the 1960-96 civil war, the red-bereted Kaibil fighters were made to eat raw dog guts as part of their training. They were accused of massacres during the war, which left more than 200,000 dead.

More recently, beheadings of policemen and drug rivals in Mexico have been blamed on ex-Guatemalan soldiers working with the Zetas, a renegade unit that broke from the Mexican army to serve as the Gulf cartel’s enforcement arm.

The Zetas have used brazen advertising along the northern U.S.-Mexico border to recruit foot soldiers, stringing banners from bridges over main roads in the towns of Reynosa and Nuevo Laredo offering well-paid jobs.

Some 75 percent of the cocaine leaving Colombia is smuggled through Central America and much of it ends up crossing the porous Guatemalan-Mexican border. Drug planes land on secret jungle landing strips and trucks move the cargo north to the United States.

President Felipe Calderon is cracking down on Mexico’s drug gangs, deploying thousands of police and soldiers to hot spots around the country. Drug violence in Mexico has killed more than 900 people this year.