FBI JOINS IN SEARCH FOR MASS GRAVES.

Byline: Lowell Bergman and Tim Golden The New York Times

Mexican authorities, working with a team of FBI agents, began to excavate sites near the Texas border Monday that they believe may hold the bodies of scores of Mexicans and Americans who disappeared in the last several years and who are thought to have been killed by drug traffickers.

The search for bodies, an American law enforcement official said, was spurred by a tip from an informant recruited by the FBI, who acknowledged complicity in several killings and identified the locations of what he said were at least two mass graves on the outskirts of Ciudad Juarez, the Mexican city just over the border from El Paso.

The informant, a former Mexican police officer, said as many as 200 people might be buried in several graves. An American official said the informer had passed a lie detector test.

The informant told American investigators that many of those killed had been providing information to the FBI and other American law enforcement agencies.

Mexican and American officials said the digging began Monday and that, as yet, no human remains had been recovered. Officials said that while they find the informer's claims credible, and they have confirmed that many of informants for the FBI, drug agencies and Customs Service have disappeared in recent years in mysterious circumstance, they have no independent corroboration that drug traffickers killed so many people.

In recent years, while murders have occurred in Ciudad Juarez by the hundreds, scores of other people have simply vanished from the area, sometimes after being seized in broad daylight by men dressed in the uniforms of Mexican federal or state police forces or the military.

Prosecutions of Mexican drug traffickers along the Texas border have also been undermined by the disappearances of witnesses and informants, some of whom have been kidnapped from American soil.

According to American officials, some of those missing had no apparent connection to the drug trade.

The Mexican Attorney General's Office, the country's chief law enforcement arm, issued a statement Monday night confirming the search for bodies, which was first reported by CBS News.

``This investigation is focused on resolving a series of assassinations and disappearances related to drug trafficking, perpetrated against Mexican and United States citizens, apparently by members of the so-called cartel,'' the attorney general's statement said. ``Over the last four years and possibly longer, in Ciudad Juarez, Chihuahua, citizens of both nationalities have disappeared without a trace.''

The Mexican authorities said they had set up toll-free telephone lines in both countries for relatives and others with information on missing people. The numbers are [phone] and [phone].

Prodded by citizens in both countries, including the Association of Relatives of Disappeared Persons, the Mexican authorities carried out a long inquiry into the disappearances but had little success.

In January, the Mexican attorney general, Jorge Madrazo Cuellar, acknowledged that drug traffickers had infiltrated a police agent into the special unit that was investigating the disappearances.

The informer who described the killings to the FBI said some had been carried out by Mexican federal policemen who worked as hired assassins for the drug gangs that operate from Juarez, which is one of the main gateways for cocaine and other drugs being shipped through Mexico into the United States.