The Cook Islands immigration minister says illegal workers are placing a financial burden on the country.
Wilkie Rasmussen says some of them have taken jobs or set up businesses that locals could do, which is in breach of the entry permit governing foreign workers.
Mr Rasmussen says the department is trying to determine who pays for illegal workers to get deported.
"In many cases a contract has been entered between employer and employee, and that becomes a determining factor about liabilities. What we are working with is that we need to identify clearly who is liable to pay for the airfares of some of these people to go back."
The Cook Islands immigration minister, Wilkie Rasmussen