According to an official, withholding a worker's passport or wages is a practice of suspected human trafficking in Saudi Arabia.
"Some identification documents, such as passports, are withheld," said Mohammed Al Masri, secretary general of the National Committee to Combat Human Trafficking.
Saudi television Al Ekhbariya reported that he said passports are personal documents that can't be kept illegally.
Withholding wages is another offence. Al Masri described work as a service for a fixed duration in exchange for a wage.
Human trafficking, according to him, is the act of obliging a worker to do an uncontracted job.
Human trafficking is punishable in Saudi Arabia by up to 15 years in prison and a maximum fine of SR1 million.
Under King Salman and Crown Prince Mohammed, Saudi Arabia has sought to reform its justice system in recent years.
A large number of migrant workers live in the kingdom.