LOS ANGELES (AP) _ Some of the record 20 tons of cocaine seized last week apparently was stored earlier in warehouses in El Paso, Texas, and across that city's border with Mexico, drug enforcement officials said.

Seven men arrested in the case - four in Los Angeles and three in Las Vegas - were expected to be arraigned before federal magistrates today.

On Friday, the day after investigators stumbled upon the Los Angeles warehouse, officials raided six warehouses in El Paso and three homes in Juarez, across the Rio Grande.

''We feel these warehouses were used as staging warehouses before the cocaine was sent to Los Angeles,'' said U.S. Drug Enforcement Administration special agent Phil Jordan.

Police said the four suspects held in suburban Los Angeles so far had thwarted investigators' attempts to identify them, giving false names and birthdates and saying only that they were from Mexico. Mexican police were said to have the identity of at least one of the men.

''We really don't know who they are ourselves,'' said police Sgt. Mike Leinen of Huntington Park, where the cocaine was found. ''They're not too forthcoming.''

Authorities believe the men are Mexican or Colombian, Jordan said.

Investigators believe one of those arrested in Las Vegas, Carlos Tapia Ponce, may have directed the ring's operations, authorities said. DEA spokesman Ralph Lochridge said Tapia Ponce worked as a customs inspector for the Mexican government in Juarez for 15 years.

''He is the person who rented the warehouse. He paid the bills,'' said Curt Hazell, a deputy Los Angeles County district attorney.

Tapia Ponce, 68, was arrested at the Flamingo Hilton hotel in Las Vegas, with his son, Eduardo Tapia Ponce, 34, and his brother, Hector Tapia, 66.

Investigators said the cocaine entered the United States through El Paso before it was shipped to the warehouse operating as Adriana's Pottery Warehouse, where the the record seizure was made Thursday.

One link between the suburban Los Angeles seizure and a house in Juarez was confirmed when one of the suspects arrested in California telephoned the house from jail. A police officer there answered the phone, Jordan said.

He said Mexican Federal Judicial Police know the identity of the caller.

No arrests were made at the house, but a tractor and two trailers fitted with secret compartments were seized. ''In one of these compartments we found 500 pounds of marijuana,'' Jordan said.

DEA agents in El Paso also found boxes similar to those found in the California raid, along with Mexican pottery.

The cocaine seizure attracted so much attention that crowds showed up at the unguarded California warehouse and began removing its remaining contents only hours after the cocaine was removed.

About 50 looters snatched up Mexican pottery, paintings, statues, desks, chairs, telephones and other office supplies.

No looting arrests were made, and no evidence was taken, police said.