The social media giant is approaching a deal to take four buildings near King's Cross station, according to The Times.
In total, the planned development is expected contain 65,000 square metres of office space, tripling Facebook's footprint in the capital.
The new offices would be located to the north of the Central Saint Martins art school, which occupies a former 19th-century warehouse renovated by Stanton Williams.
The latest details follow rumours in late 2017 that the company was in negotiations with developer Argent to develop its London headquarters at King's Cross. Argent would not verify the reports.
Facebook is "immune to Brexit"
The Times' source speculated that the new campus would be used as "growth space", rather than to relocate existing employees in London.
"They simply do not have the people to put in there yet — it's growth space. These guys are immune to Brexit and they need to be in London because that's where the talent is. It's about the availability of buildings that can be delivered to their timetable in a cool location," a source told The Times.
Facebook would be the latest tech firm to on the King's Cross development to the north of the station.
Google is also building a vast new headquarters on the site. Designed by Bjarke Ingels and Thomas Heatherwick, a planning application for the 93,000-square-metre office for 7,000 employees was submitted in 2017.
Facebook's architect not yet known
It is not known if an architect is attached to the new Facebook London HQ, which is in the early stages of development.
In 2015, Facebook moved into its new Frank Gehry-designed Silicon Valley headquarters. The 40,000-square-metre office, which claims to have "the largest open floor plan in the world", is topped with a huge rooftop park.
Gehry also designed one of the company's London offices near Oxford Street and fitted out its Irish headquarters in Dublin.
The development of the King's Cross site has seen has been progressing rapidly developed over the past ten years and recently Duggan Morris completed an office block with a millennial-pink exterior. Heatherwick is also currently converting a Victorian coal yard to create a canal-side shopping centre.