Four dozen people accused of taking part in an immigrant trafficking ring have been indicted on human smuggling and money laundering charges, authorities said.

The group brought in as much as US$130,000 a week moving people from Naco, Mexico, to its center of operations in Phoenix and then to destinations across the U.S., Phoenix police Lt. Vince Piano said Thursday.

Piano said the ring was believed to be one of the biggest operating in Arizona, the busiest illegal entry point into the country.

"It's not the end of the game, but we believe we have made some very important intelligence directions in the fight against the smugglers," said Arizona Attorney General Terry Goddard, whose office was prosecuting the case.

Ten of the 48 suspects were arrested. An additional 10 people who are expected to face charges in the future also were netted in the sweep, authorities said.

The investigation led to the discovery of 13 "drop houses" in Phoenix where human smugglers hold customers until they pay up and are sent to their final destinations. The area is believed to have about 1,000 drop houses.

Authorities allege that two Cuban immigrants living in the area, 41-year-old Jose Luis Suarez-Lemus and 35-year-old Roel Ayala Fernandez, ran the ring and paid people in Mexico and Arizona to help smuggle immigrants.

"The police just came in the house and found no proof," said Suarez-Lemus' stepson, Daril Hidalgo, who answered the phone at the accused smuggler's home and whose name was not mentioned in the redacted indictment released to reporters. Hidalgo said he did not know the name of Suarez-Lemus' lawyer.

It was not immediately clear whether Fernandez had a lawyer. He did not have a listed phone number.

The two paid recruiters in Mexico to find customers, Mexican police to allow smugglers to stage their crossings and trail guides to lead immigrants through a conservation area in southeast Arizona, Piano said.

Drivers were paid to bring the immigrants by van to Phoenix, and other drivers were used to spot law enforcement vehicles and protect rival smugglers from forcing them off the road in an attempt to kidnap and extort their customers, he said.

Once the immigrants were in a drop house and payments were made, drivers were hired to bring immigrants to spots across the country, authorities said.

They said the group would move four to six loads of immigrants per day, each with six to 10 people. Smuggling fees averaged US$2,500 per person.