Three more bodies were found Saturday on an abandoned ranch about 1,000 yards south of the U.S. border, bringing to 12 the number of dead in a suspected drug ring reprisal, officials said.

Also Saturday, a spokesman for the Sonoran Attorney General's office said authorities believe an American is behind the killings. Spokesman Jose Luis Peraza also said two people have been detained for questioning.The three bodies were found in a well where five other victims were found earlier in the week, said Tom Petropoulos, a homicide detective with the Pima County (Ariz.) Sheriff's office. Four other bodies were found in a nearby septic tank.

Petropoulos said the three bodies found Saturday were all Mexican men believed to be in their 20s and all showed signs of being strangled.

Petropoulos, who has been assisting Mexican officials in the investigation, said earlier he had never seen anything like a bathroom in an abandoned house on the ranch where some of the victims were believed to have been tortured.

"There's a strong smell of death in the air. It's a very terrible thing, a very gruesome scene. Blood was splattered and strewn, you can tell there was a lot of suffering here," Petropoulos said.

This Mexican border city of about 75,000 residents has emerged over the past two years as the center of "Cocaine Alley," because of the increased drug trafficking through the area.

Mexican officials say they believe the slayings are drug related, but stopped short of connecting the slayings here with the mass murder of five men in Tucson last weekend.