Emergency services were called to a premises at the Houston Industrial Estate in Livingston at around 8.50am on Thursday following a report of a hazardous material spill.
Scottish Fire and Rescue Service (SFRS) said it mobilised two appliances and specialist resources to the scene.
Police have also closed roads from the Houstoun Road Interchange to Nettlehill Road, Firth Road and Grange Road.
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The industrial estate has been evacuated as a precaution, with members of the public urged to avoid the area by the emergency services.
It is currently not known what the potentially hazardous material is and there has been no reported injuries.
An SFRS spokesperson said: “We were alerted at 8.38am on Thursday, March 26, to reports of a hazardous material spill at Houston Industrial Estate in Livingston.
“Operations control mobilised two appliances and specialist resources to the scene.
“There are no reported casualties and crews remain on scene.
“Members of the public are advised to avoid the area due to road closures in place from the Houstoun Road Interchange to Nettlehill Road, Firth Road and Grange Road.”