Twelve police officers accused of firing on a U.S. embassy vehicle and wounding two embassy employees must remain in detention, a judge ruled Monday. 

The incident has roiled U.S.-Mexican relations and drawn fresh attention to serious problems inside Mexico's premier law-enforcement agency. 

Mexican and U.S. officials have offered sketchy official accounts of the shooting that do not address the possible reason why Mexican federal police opened fire Friday on an armored sport-utility vehicle with diplomatic license plates carrying a Mexican Navy captain and two employees of the country's closest ally.

The federal police officers were ordered detained under a form of house arrest for 40 days on suspicion of abusing their authority. That charge can entail both criminal wrongdoing and extreme negligence. That leaves open the possibility of both a deliberate attack on the Americans by corrupt officers and a gross error by well-intentioned but trigger-happy police operating in a dangerous area.

Experts said that either scenario was cause for pessimism about the federal police, which has long been touted as the best hope for Mexico's gaining control of its struggle with organized crime.

"We're looking at another example of why there's significant concern over how Mexico has gone about training its federal police," said Samuel Logan, director of the security consulting firm Southern Pulse.

Mexican municipal and state police are seen as widely corrupt, incompetent or both. Military troops have been accused of an increasing number of human rights violations since President Felipe Calderon sent them into the streets in late 2006. Largely as a result, Mexico's government has made a large-scale effort in recent years to retrain the federal police, purge its ranks of corrupt officers and increase its numbers from 6,000 to more than 35,000 officers.

"They have been pushed to do a lot in a very short time and they are recruiting a lot of young people and they try to push them through the training process very quickly to use new equipment, and to handle new intelligence and to handle operations that are probably better handled by well-seasoned veterans," said Dr. Tony Payan, an expert on Mexico's effort to combat drug cartels and visiting fellow at the James A. Baker Institute for Public Policy at Rice University.

The reputation of the federal police suffered serious damage in June after two federal police officers fatally shot three colleagues at Mexico City's international airport. Authorities said the shooters were part of a trafficking ring that flew in cocaine from Peru. Mexico announced this month that it was replacing 348 federal police assigned to security details at the airport in an effort to quash drug trafficking through the terminal.

Last year, a businessman from Ciudad Juarez, across the border from El Paso, Texas, accused a group of 10 federal police officers of beating him, torturing him and driving him around town. They released him when he said he would get the money they were demanding.

But instead of getting the cash, used auto parts businessman Eligio Ibarra Amador went to authorities and the federal agents were detained.

In April, Ibarra was stabbed to death inside his home, which was then set on fire. Assailants killed the businessman a day before he was to attend a judicial hearing to ratify his accusation against the officers.

In the case involving the embassy vehicle, U.S. and Mexican officials declined requests for comment on Monday.

Relatives and supporters of the detained cops gathered Monday outside prosecutors' offices in the city of Cuernavaca, just south of Mexico City, to protest their detention. Waving placards and shouting slogans, the relatives briefly blocked the vans that were to take the officers to a house-arrest facility in Mexico City.

The relatives claimed the officers were simply doing their jobs in setting up a dragnet for criminals. The protesters later allowed the vans carrying the detained officers to leave for the capital.

The U.S. Embassy in Mexico City said Monday that two U.S. government employees and a Mexican Navy captain were heading to a training facility outside the city of Cuernavaca when they were ambushed by a group of gunmen that included federal police. The Mexican government said federal police were conducting unspecified law-enforcement activities in the rural, mountainous area known for criminal activity when they came upon the car, which attempted to flee and came under fire from gunmen in four vehicles including federal police.

Both countries have declined to offer further details, but experts said the incident would almost certainly affect the thinking of President-elect Enrique Pena Nieto, who has promised to both double the ranks of the current federal police and start a new paramilitary force known as the gendarmerie composed of former military members operating under civilian command.

Observers have predicted that the creation of the new force will increase tensions between the many agencies currently responsible for law-enforcement and public security in Mexico.

"The federal police have been busy for six years creating this image of the federal police as Mexico's modern police force, a police force that responded to a high set of standards, that was well-trained, well-vetted," said Alejandro Hope, a security analyst and former official in Mexico's CISEN intelligence agency . "Clearly the next administration will want to look closely at internal controls. This does not strengthen the case against a new national police force."

A Pena Nieto spokesman declined to comment on the case.

Since 2008, the U.S. government has given $243 million in equipment and $25 million in technical assistance and training to the federal police under the drug-war aid program known as the Merida Initiative.

Under Merida, the State Department says more than 4,300 federal police have completed training at Mexico's Federal Police Academy in San Luis Potosi. Taught by law enforcement professionals from the U.S., Colombia, Spain, Canada, and the Czech Republic, the program includes criminal investigative techniques, evidence collection, crime scene preservation, and ethics.

Congressman Henry Cuellar, a Texas Democrat closely involved in U.S./Mexican-relations, urged U.S. taxpayers to be patient with the development of Mexican law enforcement.

"We're seeing that in Afghanistan, Iraq, the training part of it does take a while," he said. "I am optimistic that Mexicans want to have a peaceful existence where they're free of drug violence. We need to have a long-term commitment and we need to understand it's going to be years."

Based on reporting by the Associated Press.

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