The premises have been closed immediately and its facilities will be deep cleaned, it said.
The closure comes after an employee from Facebook's Singapore office, who has been diagnosed with coronavirus, visited the company's London premises.
That person was last in a London office on 26 February, Facebook said.
“An employee based in our Singapore office who has been diagnosed with COVID-19 visited our London offices February 24-26 2020," a Facebook spokesperson said.
"We are therefore closing our London offices until Monday for deep cleaning and employees are working from home until then."
Anyone who had direct contact with the person involved has been asked to self-isolate and be vigilant in watching for symptoms.
Facebook is also contacting other employees and workers who have visited its London offices in recent days.
Facebook has more than 3,000 employees in its three offices across London.
The company is just the latest London firm to close down offices in an attempt to stop the spread of coronavirus. Other major firms including Deloitte have sent workers home following contact with people found to have tested positive for the disease.
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