Emergency services attended the incident at Macrae Edinburgh, part of Young’s Seafood, on the Starlaw Park industrial estate in Livingston at about 2:30pm.
The Scottish Ambulance Service dispatched one ambulance, a manager and its special operations response team to the scene.
During the incident, two of Young’s employees sustained minor injuries and were been taken to St John’s Hospital for treatment. A further two admitted themselves to hospital later in the day.
‘Evacuated and fully cordoned off’
A Young’s Seafood spokesman said: “The site has been evacuated and fully cordoned off, as a precautionary measure, and will remain as such until we have received confirmation by the Fire and Rescue Service that it is safe for our employees to re-enter the building.
“We are currently liaising with the Fire and Rescue Service and implementing our investigation plan and cannot comment further until we have concluded our investigation.”
Young’s expected production at the site to resume tomorrow and was providing support to its employees while investigations continued.
The past two months also saw chicken firm Moy Park and value-added vegetable processor Axgro Foods evacuate workers from their factories, following chemical incidents.
Incident at the chicken plant
In October, workers were evacuated from the Moy Park factory in Ashbourne in Derbyshire and two were hospitalised, after a possible chemical incident at the chicken plant.
Paramedics treated 35 workers at the factory, while two patients were taken to Royal Derby Hospital with minor ailments by a non-emergency ambulance.
Meanwhile, last month, bosses at Axgro insisted health and safety was their “number one priority” after a chemical incident hospitalised 11 staff. An accidental mix of chemicals, believed to be cleaning fluids, was said to be behind the incident.