Although those employees of your company may not be covered by the Employment Act, but Section 11 as quoted below may be of some guidance to you. For those whose service you no longer required, you may let them know that their contract will end on expiry and will not be renewed.
"11. Provision as to termination of contracts.
(1) A contract of service for a specified period of time or for the performance of a specified piece of work shall, unless otherwise terminated in accordance with this Part, terminate when the period of time for which such contract was made has expired or when the piece of work specified in such contract has been completed."