Death Threats Against Police Appear in Mexico Border City

Police were on alert Wednesday after several signs appeared across this violent border city warning that more officers would be killed unless the police chief resigns, a day after the second-in-command and three other officers were slain.

Meanwhile, coroners conducted autopsies on the bodies of the four officers, including the city police chief's right-hand man, Sacramento Perez, the operations director for the 1,700-member force.

Gunmen ambushed the officers Tuesday afternoon while they were sitting in their patrol car on a street near the U.S. consulate. No arrests have been made.

About 50 police officers have been killed in the past year in attacks blamed on drug gangs trying to consolidate territory. Many officers have quit out of fear for their lives, often after their names have appeared on hit lists left in public in Ciudad Juarez, across the Rio Grande from El Paso, Texas.

At least four cardboard signs with handwritten messages appeared on the doors of businesses Wednesday morning, warning that one police officer would be killed every 48 hours if Public Safety Secretary Roberto Orduna did not resign, said Daniela Gonzalez, a spokeswoman for the state Attorney General's office.

Mayor Jose Reyes Ferriz gave a news conference pledging to support Orduna, who has not made a public appearance since the killings. Ferriz put the force on "red alert" Wednesday, meaning no officer can patrol alone in the violence-plagued city of 1.3 million.

Orduna took over the post in May after former Police Chief Guillermo Prieto resigned following the slaying of his operations director.

Drug gangs have unleashed unprecedented violence since the Mexican government launched its national crackdown on organized crime in 2006. More than 6,000 people have been killed in drug violence across Mexico. More than 1,600 have been killed in Ciudad Juarez, the country's deadliest city.

In another northern border city, Reynosa, video footage aired on Wednesday showed masked policemen evacuating children from a school with some of the students wearing bulletproof vests, during an hourslong gunbattle Tuesday that left five gunmen dead and seven police injured.

The battle lasted several hours, terrorizing residents who dropped to the ground or fled indoors.

Also Wednesday, police reported finding the bound and bullet-ridden bodies of two men in a car in the Pacific coast resort town of Zihuatanejo.

Homicide rates have soared as drug cartels battle each other and the army, and soldiers have been accused of abuses against civilians.

Mexican Economy Secretary Gerardo Ruiz Mateos on Wednesday defended the government's decision to send 45,000 soldiers across Mexico to fight the cartels. His comments came a day after hundreds of people blocked bridges to the United States to demand that the army withdraw.

Ruiz Mateos predicted that if Mexico gave up its fight against the cartels, "the next president of the republic would be a drug dealer."

He made the comments during a visit to Paris. They were broadcast in Mexico by W Radio.