The children, both aged 17, were located in two stores in the Halifax area, where they were found in the company of staff who were working.
Neither child has any parents or relatives in the UK and it is thought they were the victims of Human Trafficking Gangs, with one entering the county at the age of 15.
West Yorkshire Police today said the children had been found during the course of a four-day operation which began on July 2.
Detectives led by Detective Sergeant Michael Richmond, of Calderdale CID, joined the Halifax and Calder Valley Neighbourhood Policing Teams and representatives from the Gangmasters and Labour Abuse Authority (GLAA) and the charity Hope for Justice to visit a number of commercial premises across the Calderdale district.
Both children have since entered the National Referral Mechanism for suspected victims of modern slavery and are in the care of social services.
Children’s social care has secured safe placements for the young people as emergency childcare.
Detective Chief Inspector Dave Shaw, of Calderdale District Police, said: “Human trafficking is an evil crime which trades in human misery.
“We have been speaking to the staff at the various premises who have shared some horrific stories of being moved across continents, staying in migrant camps and travelling to the UK in the backs of trucks.
“Many have said that they felt they were under the control of organised crime groups. The two children we have rescued appear to be happy to have been taken out of such an environment – some indicated they were being paid less than the minimum wage and that their earnings were topped up with food and accommodation.
“To show the lengths the criminals will go to we found one victim who had been branded to indicate she would forever be the ‘property’ of a particular gang.”
During the operation, officers spoke to 36 members of staff at eight premises about their immigration status.
Det Chief Insp Shaw said: "Once it was confirmed that there was no suspicion that they had been trafficked, five males were arrested for being in the UK illegally.
"They were subsequently passed on to Immigration Enforcement for further action."
As well as rescuing the two victims, the team gathered information and intelligence which is being shared with Government agencies including Immigration Enforcement, HM Revenue and Customs and the Department of Work and Pensions.
“The gangmasters behind this vile trade may be organised – but so are we," Det Chief Insp Shaw said. "By working together on operations like this and by sharing information with relevant partners we can make a real difference.”
He also urged residents using cash-only businesses to think twice about where there money was going and what it could be funding.
Call police on 101 or the Modern Slavery Helpline on 08000 121 700 to report any suspicions about human trafficking or modern slavery.