Poop-testing startup uBiome just filed for bankruptcy. Some of its largest creditors are health insurers saying they're owed millions in refunds.

uBiome; Yutong Yuan/Business Insider

uBiome founders and former co-CEOs Zac Apte and Jessica Richman. uBiome just filed for bankruptcy.

• Poop-testing startup uBiome just filed for bankruptcy and put its assets up for sale.
• The company was raided by the FBI earlier this year, reportedly over its billing practices, and its troubles continued to mount.
• Many of the biggest claims against uBiome are from health insurers requesting refunds, according to the bankruptcy filing. Three of the claims exceed $1 million.
• Those claims are listed as disputed, suggesting that uBiome and the creditors either disagree about the claim entirely or the amount of the claim.
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Poop-testing startup uBiome just filed for bankruptcy.

uBiome was raided by the FBI earlier this year, reportedly over its billing practices, and problems at the beleaguered company have continued to build since. The startup will continue to operate while it works to sell its assets, it said in a Wednesday statement.

Some of uBiome's largest claims from creditors are refunds requested by health insurers, according to the company's Wednesday bankruptcy filing. The filing names the creditors with the 30 largest unsecured claims against the company.

The list includes some of the biggest names in the business, like Cigna and UnitedHealth, and employees in charge of fraud and investigations are named as points of contact for the claims.

The filing notes that these claims are disputed, meaning that the two parties may disagree either about the claim itself or its size.

The bankruptcy filing was first reported by The Wall Street Journal.

Read more: uBiome convinced Silicon Valley that testing poop was worth $600 million. Then the FBI came knocking. Here's the inside story.

Other claims against uBiome are from companies saying they're owed for professional services. Yet many are from health insurers or government health programs saying they're due refunds.

Here are some of the biggest ones and most well-known names:

• Health insurer Cigna, which says that uBiome owes it about $2.1 million in a "refund claim." The claim is noted as disputed and a fraud specialist at Cigna is listed as the point of contact.
• Health insurer UnitedHealth, which claims that uBiome owes it $2.08 million, also a "refund claim" that's disputed. An "investigations and settlement consultant" at the health insurer is named as the creditor contact.
• Health insurer Horizon Blue Cross Blue Shield of NJ. It claims it's owed a refund of $1.4 million, which is also contested.
• Health insurer Blue Shield of California, which claims it's owed an about $425,000 refund. This is also listed as disputed. The health insurer's contact person on this claim is listed on LinkedIn as an investigator at the insurer's special investigations unit.
• Military health insurance program Tricare West, which says it's owed a refund of about $404,000. This is also listed as disputed. The bankruptcy filing lists two additional, separate claims from Tricare and Tricare South, also contested.
• Health system Kaiser Permanente's Kaiser Foundation Health Plan, which says it's owed about $271,000 in a refund claim, which is also disputed.
• Health system Mayo Clinic's health plan, which claims it's owed about $96,000 in a refund claim. This one is also disputed.
• Health insurer Harvard Pilgrim. It claims it's owed about $83,000 in a refund claim, which is also contested.