Earlier this month, the Palo Alto, California-based company reported that the funding round, which started in July, had raised $679.8 million. Wednesday's filing indicates it raised an additional $200 million in just weeks.

Founded in 2004, Palantir, which is considered Silicon Valley's most secretive company, does highly confidential work for U.S. defense and intelligence agencies. Its data mining system, which uses algorithms to search for patterns and connections, helped the U.S. government track down al Qaeda leader Osama bin Laden.

The company's large staff of consultants also work with large businesses, police departments, banks and branches of the U.S. military.

Palantir has raised close to $2 billion from investors. Its valuation earlier this month reached $20 billion, up from $15 billion in late 2014, making it the fourth-highest-valued, venture-backed private tech company in the world.

The company has bucked growing skepticism among late-stage investors about plowing millions into highly valuable companies. Other 'unicorns,' or venture-backed companies ostensibly worth $1 billion or more, have watched their valuations come under heightened scrutiny.

Palantir's strong government ties and an annual revenue estimated by some at more about $1 billion likely set it apart from other cash-burning startups. The company was co-founded by Peter Thiel and Joe Lonsdale, two of Silicon Valley's more influential investors and entrepreneurs.