Federal agents raided a migrant farm labor camp (search) where homeless men and women were kept in what labor officials called a version of modern-day slavery.

Four people, including the camp's owner, Ronald Evans, face federal charges in a case that officials said is likely to grow. Investigators are looking into alleged environmental violations and drugs found at the camp in Friday's raid.

"The word is out that we are concerned about human trafficking, and we will leave no stone or camp unturned," said Steve Cole, a spokesman for Jacksonville U.S. attorney Paul I. Perez.

Officials said homeless people were recruited to the Evans Labor Camp (search) through offers of room and board, along with alcohol, tobacco and drugs, which they bought on credit. But they never made enough in the field to pay it off, according to an investigative summary.

"A lot of times, they get them indebted even before they get back to the camp," said federal agent Rebecca Hall.

In a small central shed, investigators found about 100 rocks of suspected crack cocaine along with cigarettes and beer. Detective Lt. John Merchant described the shed as a "shop" where the rocks were sold for $20 each.

Department of Labor agents were joined in the raid by local officials and agents from the Environmental Protection Agency, which was investigating illegal dumping of raw sewage into a tributary of the St. Johns River.

"They've found what clearly looks like EPA (search) violations, discharging raw sewage into the environment," said Putnam County Sheriff's Capt. Gary Bowling.

Seventy-eight potato field workers were interviewed at the compound south of Jacksonville. Some were arrested on unrelated, outstanding warrants.

Federal civil rights attorneys waited outside the camp to talk to the workers, offering them help getting out of the camp and finding other work. About 20 left with the attorneys.