Two suspects were being sought.
Some of the victims were beaten with an aluminum baseball bat found at one of the scenes, and at least one victim was shot, Colquitt County Sheriff Al Whittington said.
The attacks took place in southern Georgia, about 180 miles south of Atlanta. Three were in Tift County; a fourth was in neighboring Colquitt County.
"We think they're tied together," said Colquitt County Sheriff's Capt. Hal Suber.
All the dead were immigrants from Mexico, and all but one belonged to the same family, according to Francisco Dominguez, who said his uncle and a cousin were killed in their trailer on the outskirts of town.
"He came here to work and here is where he died," Dominguez said. "He should have gone out to build chicken houses this morning."
Whittington said the attacks might be linked to other robberies of immigrants in the area over the past two weeks.
Immigrants "carry large sums of cash and that makes them an easy prey," the sheriff said. "I don't think it has anything to do with race or hate."
Among the wounded, at least two were in critical condition, said Mike Lewis, a Georgia Bureau of Investigation agent.
In the Colquitt County attack, a man was shot in the head and beaten with a baseball bat, and his wife was hit in the mouth, Suber said. The man was in stable condition. Suber said it appeared the woman would be OK.