Voodoo-practicing drug smugglers killed at least 12 people, including an American college student, in the belief the slayings would bring demonic protection to their illegal activities, officials said Wednesday.

Twelve bodies were discovered in a mass grave Tuesday on a ranch just below the U.S. border, 20 miles from Matamoros. The bodies were mutilated, and authorities said they found candles and kettles full of body parts and animal bones."Very clearly they believed the human sacrifices and the animal sacrifices put a magical shield around them that protected them from evil or harm, even up to bullets," Texas Attorney General Jim Mattox said Wednesday.

Sheriff Alex Perez of Cameron County, Texas, said the scene was "like a human slaughterhouse." Police continued digging for two more bodies believed buried at the ranch.

Mexican officials said five men have been arrested in the case, but U.S. officials listed only four. Authorities on both sides of the border are seeking the alleged ringleader, Adolfo de Jesus Constanzo, a Cuban in his late 40s.

At least one victim was kidnapped in Brownsville within the past month, and as many as three of the dead may be American, officials said.

The dead included 21-year-old University of Texas student Mark Kilroy, who vanished last month in Matamoros while on spring break, Sheriff's Lt. George Gavito said.

Kilroy apparently was chosen at random after the cult members "were told to pick one Anglo male that particular night," Gavito said.

Authorities would not identify the other victims but said all were males. Some victims were shot in the head, and others appeared to have been slain with machetes or sledgehammers, said Oran Neck, chief U.S. Customs agent in Browns-ville.

Suspects in Mexican custody have told police of 14 human sacrifices, and evidence indicates there may be more, Neck said.

Constanzo apparently introduced a sort of voodoo or black magic to the area, Neck said. The ritual "has overtones of a religious cult that has been exported out of Cuba and Haiti as `San-teria,' " Neck said.

Perez said that the cult members removed some of the victims' vertebrae to use them for necklaces and that investigators had also found bowls and a caldron from which brains, hearts and other organs of victims were eaten.

Felipe Flores, spokesman for the Mexican attorney general's office, said that during the ritual killings, victims' brains were cut out and put on a fire, mixed with blood, herbs, roosters' feet, goats' heads and turtles.

The Mexican attorney general's office described Constanzo as a "godfather" to members of the voodoo-practicing sect and said he is believed to have fled to the United States. Mattox said the cult is believed to have had 10 members.

"Mark's with God - no problem. We can accept that. If he had died of a drug overdose or in a robbery, we couldn't have accepted that."

Kilroy, a premedical student, vanished from a crowded Matamoros street shortly after 2 a.m. on March 14 after drinking with a group of friends in the city of 180,000 just across the Rio Grande from Browns-ville.

The 3-foot-deep grave containing his body was found after federal police alerted U.S. officials they had obtained confessions from the suspects, officials said.

It was the third drug-related mass killing discovered along the U.S.-Mexican border within three weeks. The bodies of nine men and three women were found March 29 and April 1.