The authorities in Texas have charged two men with conspiring to harbour suspected illegal immigrants.
It follows the discovery of 115 people locked inside three small houses in Edinburg, close to the Mexican border.
Police were alerted by a call made from inside one of the houses. The property was found to have padlocks and chains on the outside.
People found inside said they had not had any food or water for three days, and some required hospital treatment.
Oscar Trevino, an Edinburg police spokesman, told the BBC that it was clear the people in the properties were being held against their will.
"There was no way that they could leave because the doors were secured with burglar bars and were locked from the outside."
He said officers had to use bolt cutters to free those inside.
The imprisoned people came from several different countries in south and central America.
One man told officers that they had been driven to the houses from the Rio Grande river, which marks the border between Texas and Mexico.
He said they had been threatened with death if they did not remain quiet.