Route for Cocaine Outlined in Report : Drugs: A DEA intelligence document tells how a record 21-ton haul seized last fall was brought across the border in the trunks of cars.

The record 21 tons of cocaine seized at a San Fernando Valley warehouse last fall was smuggled across the U.S.-Mexico border at El Paso, 650 pounds at a time in the trunks of Mercury Marquis automobiles, according to an intelligence report obtained by The Times.

After being stockpiled in the Texas border town, the cocaine was then shipped to Los Angeles in refrigerated big rigs in massive loads of several tons each, according to the Drug Enforcement Administration document.

The authoritative account differs sharply from previous reports, in which investigators theorized that the Mexican operatives who masterminded the operation evaded U.S. border guards by hiding their cocaine in hard-to-search commercial vehicles or dividing it among human “mules” who crossed into the United States illegally.

Instead, the DEA report indicates, the cocaine brought into the United States by the mammoth smuggling operation was simply driven on hundreds of occasions directly past U.S. Customs agents, from whom it was shielded only by the steel lid of a Ford Motors trunk.

The document makes no criticism of Customs’ actions in the case, but a recent General Accounting Office report faulted the agency for relying on a computer database incapable of providing border agents with adequate warnings against suspicious individuals or vehicles.

“There is an increased risk that known or suspected law violators may enter the United States undetected,” the GAO report concluded.

The new details about the smuggling operation from Colombia to a Sylmar warehouse were contained in a report warning of Mexico’s increasing role as a transit point for U.S.-bound cocaine.

The report by the DEA’s Office of Intelligence asserts that the cocaine had been flown into Mexico near Juarez by Colombian trafficking organizations and was to be delivered from Los Angeles to Colombian distributors in Southern California, New York and Florida.

In a pattern that has come to be typical, it said the cross-border smuggling was “facilitated” by Mexican organizations operating as key middlemen.

The report indicated that the 21 tons recovered in Los Angeles last Sept. 28 and an additional 60 tons that had passed through the warehouse in the previous six months had been concealed “in the trunks of cars (usually Mercury Marquises) in quantities of roughly 300 kilograms per shipment and driven across the border.”

Hector Tapia Anchondo, the alleged ringleader, and six others have been arrested in connection with the smuggling inquiry. DEA spokesman Bill Ruzzamenti said that the agency could not comment on the intelligence report because the case has not yet come to trial.

The document, dated February, 1990, and marked “DEA-sensitive,” also provides new details about a wide range of other smuggling methods used to ferry cocaine into the United States in a number of huge shipments seized by American authorities last fall.

Most surprisingly, the intelligence report asserts that the nearly five tons of cocaine seized last October in a Harlingen, Tex., stash house had crossed into the United States by small rafts floated across the Rio Grande River at Bluetown, Tex.

The report describes land smuggling as “the current method of choice” and warns that “the cocaine threat at the U.S.-Mexico border is complex and multifaceted.” The document was drafted before the discovery last week of a 273-foot underground tunnel used to smuggle cocaine from Mexico into Douglas, Ariz.