Four men have been accused of being involved in a human-smuggling operation that was uncovered Thursday in north Houston.

The arrests were made after relatives of a victim contacted authorities, saying the man had been kidnapped and was being held against his will by human traffickers, said Harris County Precinct 4 Constable Mark Herman.

Herman said the man had been smuggled from Mexico to the Houston area. His family had made two payments of $950 to the human trafficking operation and agreed to pay $2,000 more when the man arrived in Houston. But when his family drove here from Maryland to pick him up and tried to pay the smugglers the agreed upon amount, the traffickers demanded $2,900 for his release. They threatened to harm the man and his family if the money was not handed over.

Posing as the man's relatives, deputy constables agreed to meet the suspects along Airline in north Houston and pay them the money in exchange for the man, Herman said. Three suspected "coyotes" were arrested when they showed up at the meeting. The man was released unharmed.

During the investigation into the case, deputies learned the man had been held at a stash house in the 14000 block of Sellers Road. Deputies went to the home and found another "coyote" and three other people who had been illegally smuggled into the country from Mexico. They had been forced to work as "slave labor."

Arrested in the case Kilmer Roberto Yanes Zavala , Weldin Yobany Ayala Soriano, and Hector Rodriguez Sanchez. They were taken into custody at the meeting with deputies.They are each charged with aggravated kidnapping and smuggling.

Heivi Martinez-Garcia was arrested at the stash house. He is charged with four counts of aggravated kidnapping.

All the suspects are being held in the Harris County jail with no bond.

Herman said deputies are investigating the case.