FREMONT — A mega tech campus that Facebook envisions in Fremont has begun to sprout — and might wind up being bigger than initially anticipated — amid a flurry of property deals being orchestrated by legendary Silicon Valley developer Peery Arrillaga.

Facebook’s presence in Fremont originated through a series of leasing deals during 2017 and 2018. These rental agreements enabled Facebook to occupy a total of 1.04 million square feet in Fremont, all in Ardenwood, a tech hub near the east end of the Dumbarton bridge.

The initial leasing transactions by Facebook in Fremont included 14 buildings totaling 750,000 square feet that Facebook rented from Peery Arrilaga and 290,000 square feet in three buildings the tech titan leased from Sobrato Organization.

The social networking titan has started construction work in recent weeks, Peery Arrillaga revealed in a cascade of public documents, on at least a dozen buildings that Facebook had leased as part of the 2018 deals with the Palo Alto-based development giant.

Separately, Peery Arrillaga has bought a big Fremont building that is set to become part of the huge jobs hub Facebook has begun to sculpt in the East Bay city, according to property records on file with Alameda County.

The building that the Peery Arrillaga firm bought near the end of October from tech company Electronics for Imaging is at 6750 Dumbarton Circle in Fremont, Alameda County records show.

Peery Arrillaga paid $38.5 million for the building, which totals 119,000 square feet, according to public records. The transaction was an all-cash deal.

The recent Facebook construction work in Fremont includes five office buildings on Dumbarton Circle, four on Kaiser Drive, and three on Campus Drive, the county documents filed by Peery Arrillaga show.

The combined size of the dozen buildings where the Facebook redevelopment work is occurring is 724,000 square feet, the LoopNet database shows.

The property records show that Facebook is a tenant in all of the buildings — including the two office buildings on Dumbarton Circle that Peery Arrillaga recently purchased.

The total size of Facebook’s Ardenwood campus now is in the range of 1.27 million square feet in the wake of the latest Peery Arrillaga property purchase maneuvers.

Additional Facebook expansions could be in the works in Fremont beyond all of this.

Peery Arrillaga also owns two other buildings, at 6800 and 6900 Dumbarton Circle, that the developer leased to Tesla in 2017. These Tesla office sites are near the building Peery Arrillaga bought in October, and across the street from other Facebook-leased offices.

Those adjacent office buildings rented by Tesla total 230,000 square feet. Tesla undertook a major renovation of the offices before moving in. After that lease deal, though, Tesla announced job cuts totaling 1,050 positions in the Bay Area, including roughly 965 in Fremont. The job cuts were completed by March 2019, state labor filings show.

In the wake of Tesla’s retrenchment, some commercial real estate sources say Tesla hopes to sublease the Fremont office buildings. If so, that could make the buildings ripe for additional Facebook expansions.