MEXICO CITY (AP) — The Mexican police officers who arrested infamous drug suspect Edgar Valdez Villarreal, alias "La Barbie," did not initially know who they had caught, according to a booking report obtained Thursday.

The Mexican government has depicted the capture of the U.S.-born Valdez as the result of a 1½-year investigation and a carefully planned raid involving agents specially trained abroad.

But a copy of the booking report obtained by The Associated Press and other media outlets indicates that while special police teams were in the area where Valdez was caught Aug. 30, the officers who actually detained him were simply following a suspicious vehicle.

The report filed by federal police with prosecutors says a police patrol was traveling on a road west of Mexico City that day when a convoy of three vehicles passed at a high rate of speed.

The officers, who were not identified in the report, followed the convoy for more than two miles (four kilometers) before the vehicles stopped and officers ordered the occupants to get out.

The first person to descend from the vehicles was "a light-complexioned man who we later learned was Edgar Valdez Villarreal," according to the report, which also says the arresting officers were coordinating patrol efforts with a special operations unit.

In a statement, the federal police said the fact that such units were participating in the operation "implies that they were focusing on specific targets," not just detaining suspects at random.

A federal police spokesman said the two versions of Valdez's arrest were not contradictory. He said the special operations group, as part of routine procedures, may not have informed all uniformed officers in the area about who exactly they were looking for.

The spokesman would not allow his name to be used, as is customary at government agencies.

Police said earlier that they had traced Valdez to a ranch in the wooded outskirts of Mexico City by tracing his assets and from information obtained following the arrest of some of his associates.

Doubts had arisen about the official version of the arrest after the alleged drug capo, known as "the Barbie" for his fair complexion and green eyes, showed no sign of fear or consternation when he was paraded before news media following his arrest. He smirked and appeared to shrug at reporters' questions.

In comments to the television network Televisa, U.S. Ambassador Carlos Pascual said he was "absolutely convinced" that the arrest was the result of a focused, long-standing investigation.

"They followed the case for a long time and they finally had success in capturing La Barbie, capturing him — and I think this is important — alive," Pascual said. "In this sense, it provides a lot of opportunities to go on exploiting any information he may have, to go after other drug traffickers."

The 37-year-old Valdez faces charges in three U.S. states for allegedly trucking in tons of cocaine.

As a U.S. citizen living illegally in Mexico, he could be deported to the United States, or he could face prosecution in Mexico for drug-related crimes. Mexican authorities say he could be responsible for dozens of murders.

The arrest was portrayed by the Mexican and U.S. governments as a victory for President Felipe Calderon, who is trying to recover public support for his war on organized crime in the face of escalating violence.