We now know the identity of some of the biggest private investors in Theranos

When Theranos was at its prime, it attracted funding from big-name investors who poured millions into the blood testing startup. Now, we're learning the identity of some of those private investors for the first time, and who stands to potentially lose big if the startup's troubled timeline can't be turned around.

The Wall Street Journal reports that Rupert Murdoch, Cox Enterprises, and Riley Bechtel of Bechtel Group, one of the largest construction companies in the world, were among Theranos' early investors. Murdoch and Cox each put $100 million into the company during its most recent funding round of $632 million, which came to a close in 2015, according to The Journal.

Murdoch is the executive chairman of the Journal's parent company, News Corp. In an interesting twist, The Journal was the first publication to report on trouble at Theranos in October 2015.

Theranos remains mired in legal battles, including a $140 million breach of contract suit filed by Walgreens earlier this month and a new lawsuit filed Monday by Robert Colman, cofounder of San Francisco investment bank Robertson Stephens & Co. The suit alleges that Theranos was misleading its investors and making false claims about its technology, according to the Journal.

Theranos also shut down its lab operations in October after the accuracy of the test was called into question, cutting 340 jobs and closing the Wellness Centers where blood tests were performed. Theranos CEO Elizabeth Holmes is now banned from the lab-testing industry for the next two years.

That setback, plus what will likely be expensive legal battles as Theranos fights the Walgreen suit, are likely to cost the company millions. The startup was once valued at $9 billion and, according to Pitchbook, has raised more than $750 million to date.