The Driver Vehicle Agency in Northern Ireland says only a limited number of tests are being carried out at MOT centres here.
Checks are being conducted on vehicle lifts in the test centres, following the identification of faults.
The Department of Infrastructure insists this is a precautionary measure to ensure the safety of staff and customers.
It expects the inspections to be completed today, and says any necessary repairs will be carried out as soon as possible.
As and when test centres have been inspected and any necessary repairs completed, they will immediately become operational.
Appointments are being rescheduled for customers affected, while Mallusk is the only test centre not carrying out car and light vehicle tests.
Heavy goods vehicles and bus tests remain unaffected.
DVA says it's making 'every effort' to contact customers to reschedule appointments, and will prioritise customers who require an immediate test.
All other test centres remain open and customers should attend their MOT appointment unless contacted by DVA.