TUCSON, Ariz. -- There's been more violence on the U.S.-Mexico border in Arizona, one of the busiest crossing points for illegal immigrants and drug smugglers.

A pickup packed with nearly two dozen suspected illegal immigrants and smugglers was ambushed by gunmen early Friday in southern Arizona.

Authorities said a man and a woman were killed and at least one other person was wounded in the attack about 20 miles south of Tucson.

The assailants thought the pickup was smuggling narcotics that they had hoped to steal, authorities said. They said they based that in part on the driver of the pickup yelling out the window that he was carrying people, not drugs.

The 23 people investigators believe were in the truck included 20 members of three families from the Mexican state of Chiapas who had crossed into the U.S. on foot near Sasabe, Arizona.

Authorities said the pickup driver sped off when the shots rang out and then stopped. The passengers ran into the desert, officials said.