Two men have died and two others were after a wall collapsed at a farm near Linlithgow.
The incident happened on land at Whitecross just after 10am.
Police Scotland said two men suffered serious injuries and were pronounced dead at the scene.
One of the injured men has been flown by air ambulance to Queen Elizabeth University Hospital in Glasgow, while the other has been taken to Edinburgh Royal Infirmary.
Neither of the men in hospital are thought to have life-threatening injuries.
Several roads have been closed while investigations take place.
Chief Inspector Damian Armstrong of Police Scotland said: "My thoughts and sympathies are with the families of those affected by this incident and a multi-agency inquiry at the farm is ongoing.
"If anyone believes they have any relevant information that may be of use to this investigation then please come forward."
The Health and Safety Executive have been informed of the incident.
A fire service spokeswoman said: "The Scottish Fire and Rescue Service responded at 10.11am on Monday, May 6 with emergency service partners to a farm in the Falkirk area following reports of a collapsed wall.
"Operations Control mobilised a number of fire appliances to the Whitecross area and firefighters currently remain in attendance."
