An Post has evacuated its Merrywell parcel depot in Dublin after it was inundated by smoke and fumes from the fire at the Oxigen waste recycling plant in Ballymount.
It is expected to be at least 24 hours before staff can return to the depot, which handles parcel deliveries for south Dublin.
Parcel delivery services are expected to be disrupted as a result of the forced evacuation.
Traffic diversions and local access restrictions are also in operation at the Merrywell Industrial Estate following the major fire over the weekend.
The restrictions will remain in place tomorrow.
A forensic examination still has to be carried out to determine the cause of the fire.
A building that housed waste-processing systems has been destroyed.
Oxigen has said it will be trying to relocate as many as possible of the around 60 staff who worked in the building to other facilities nearby.
Dublin Fire Brigade had three fire crews at the scene of the blaze this morning.
A spokesperson said visibility in the area had improved.
The Environmental Protection Agency is continuing to monitor the air quality in the area.
It has advised people in the area to keep their windows closed.