Mexico's most powerful drug cartels are recruiting former Colombian soldiers, prompting Mexican authorities to turn away Colombians trying to enter the country. Last week twelve Colombians in the western state of Michoacan were arrested in connection with a mine attack that killed eight Mexican soldiers. Close underworld ties have long existed between organized crime groups in Mexico and Colombia. For many years, Colombian drug traffickers produced cocaine and heroin and moved it themselves by boat or plane to the US. Later, as US authorities cracked down on trafficking in the Caribbean, Mexican cartels' power grew as they moved Colombian drugs over land and via small plane to the US border and smuggled them across.