EL PASO, TEX. -- Authorities said they still cannot find the smuggler who locked 19 illegal aliens into a stifling boxcar where all but one suffocated.

Bill Harrington, assistant chief of the U.S. Border Patrol's El Paso sector, said 15 of the bodies have been positively identified.

Border Patrol agents said they think the smuggler, known only as "Chapulin" or "grasshopper," is Mexican and worked with two other smugglers who died in the boxcar.

Harrington said Border Patrol agents have found a Mexican address for the smuggler but he will be extremely difficult to find.

Several victims have been identified as residents of Pabellon de Arteaga, Aguascalientes. Families from Aguascalientes came to the border between Juarez, Mexico, and El Paso to look at photos that might help authorities identify the remaining men, Mexican Consulate spokeswoman Beatriz Lopez said.

The 19 men were discovered Thursday by Border Patrol agents at a railroad siding at Sierra Blanca, 75 miles southeast of El Paso.

The survivor, Miguel Tostado Rodriguez, 21, is being held in the Border Patrol Detention Center in El Paso as "a material witness" in the case against the third smuggler, Border Patrol sector chief Mike Williams said.

Donated coffins were readied to carry the bodies back to the poor Mexican communities the men had left. Mexico's government is arranging and paying for the return of the bodies because the families cannot afford the expense, said Lopez.