Gunmen armed with assault rifles and grenades attacked a convoy carrying the top security official of the western state of Michoacan on today, leaving four dead and 10 wounded in the second brazen ambush in as many days.

Public Safety Secretary Minerva Bautista was recovering from non-life-threatening wounds, said an official of the state attorney general’s office who was not authorized to be quoted by name. Bautista was travelling in a bullet-resistant sport utility vehicle.

The dead included two of her bodyguards and two bystanders. Of the nine people wounded in addition to Bautista, five were bystanders - including two girls ages 2 and 12 - and four were part of Bautista’s security detail.

There was no immediate information on the identity of the attackers, who numbered about 20, or on a possible motive.

However, drug violence is common in Michoacan, the home base of La Familia cartel.

Bautista was returning from the inauguration of a fair when her three-vehicle convoy was blocked just after midnight by a truck the attackers apparently used to block the road.

Several hours later, assailants tossed a hand grenade at a police station in the Michoacan state capital, Morelia, about 30 yards from the state public safety department’s headquarters. The explosion damaged three vehicles, but nobody was hurt.

Mexican drug cartels have been known to target security officials; the acting federal police chief was shot dead in May 2008 in an attack attributed to drug traffickers lashing back at a nationwide crackdown on organized crime.

Yesterday, gunmen ambushed two police vehicles at a busy intersection in the northern border city of Ciudad Juarez, killing seven officers and a 17-year-old boy caught in the crossfire. Two more officers were seriously wounded.

Authorities said the officers had stopped to talk to a street vendor who flagged them down for help. Gunmen suddenly opened fire from behind and then fled in three vehicles.

Hours after the attack, a painted message directed to top federal police commanders and claiming responsibility for the attack appeared on a wall in downtown Ciudad Juarez. It was apparently signed by La Linea gang, the enforcement arm of the Juarez drug cartel.

The Juarez cartel has been locked in a bloody turf battle with the Sinaloa cartel, led by Joaquin “El Chapo” Guzman.

“This will happen to you ... for being with El Chapo Guzman and to all the dirtbags who support him. Sincerely, La Linea,” the message read. The authenticity of the message could not be independently verified.

More than 22,700 people have been killed in Mexico’s drug war since December 2006, when President Felipe Calderon launched an offensive against the cartels.

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