Theranos and its founder Elizabeth Holmes have been sued by one of the blood-testing start-up's biggest backers, for allegedly lying to attract nearly $100 million in investment, the Wall Street Journal and other outlets reported.
The WSJ report said that San Francisco-based hedge fund, Partner Fund Management, filed a suit in the Delaware Court of Chancery on Monday.
The suit accused Holmes and Sunny Balwani, a former top Theranos executive, of deceiving the hedge fund by claiming Theranos had developed "proprietary technologies that worked" and were close to getting regulatory approvals, the WSJ reported.
To read the full WSJ report, click here.
Reuters reported, meanwhile, that Partner Fund Management had described the lawsuit to its investors in a letter that said, "Through a series of lies, material misstatements, and omissions, the defendants engaged in securities fraud and other violations by fraudulently inducing PFM to invest and maintain its investment in the company,"
Holmes said in a public letter this month that the troubled start-up would close all its clinical labs and retail-focused Wellness Centers to concentrate on more specialized testing technologies.
In a statement given to CNBC on Monday, Theranos said that Partner Fund Management's suit was without merit, and that it would fight the legal action vigorously.
"The hedge fund is engaging in revisionist history,making claims that are not rooted in facts," the statement said. "The company remains committed toits mission and is appreciative of its strong investor base that understands and continues to support those efforts."
Partner Fund Management did not immediately respond to CNBC's request for comment, made outside office hours.