Police carrying out human trafficking raids found a woman who had been branded to show she would "forever be the property" of a gang.
Two 17-year-old boys were also discovered during the four-day West Yorkshire Police operation targeting eight businesses in Calderdale.
Police said neither boy has parents in the UK, and one is thought to have been in the country since he was 15.
Five people have been arrested on suspicion of being in the UK illegally.
Police said they were not thought to be victims of human trafficking and are being dealt with by immigration authorities.
No other arrests have been made.
Det Ch Insp Dave Shaw said the two boys found during the raids on businesses suspected of employing victims of human trafficking are now in the care of social services.
He said during the raids, many of the 36 staff interviewed shared "horrific stories" of being moved across continents, staying in migrant camps and travelling to the UK in the backs of trucks.
"They felt they were under the control of organised crime groups," added
One woman had been branded to show "she would forever be the property of a particular gang", Det Ch Insp Shaw said.
The Calderdale region is made up of several towns, including Brighouse, Halifax and Hebden Bridge.