A dietary supplement may be the common link in a rash of hepatitis cases in Hawaii that has sickened 29 people, leaving two in need of a liver transplant and one dead, federal health officials said.

The only thing investigators have found in common between the cases so far, officials said, is that roughly four out of five of them took OxyElite Pro, marketed to burn fat, within 60 days of becoming sick.

The epidemiologic data linking the use of the dietary weight-loss supplements with liver failure and death is "compelling," said Dr. Sarah Park, head of Hawaii's Department of Health Disease Outbreak Control.

"We are actively soliciting more cases, and we are investigating what it is about this product," Park told ABC News.

Park's involvement with the cases of hepatitis began early in September, when the state's transplant center notified her of an unusual case in which a young, previously healthy individual required a liver transplant. No infectious cause of the liver failure could be identified, she said. More cases soon followed, which led Park to release a medical advisory across the state of Hawaii.

For now, nobody knows for sure what is causing the outbreak. The company that makes OxyElite Pro is USPlabs. Company officials have said they do not believe their product is at fault.

"The ingredients have been studied for safety, are consumed in the food supply and widely used in dietary supplements," the company said in a statement. "Out of an abundance of caution, the company has ceased domestic distribution of OxyElite Pro with the Purple Top and OxyElite Pro Super Thermo Powder until the investigation has been completed. The company continues to believe these versions are safe and are not the cause of the cluster of liver toxicity that has occurred in Hawaii."

The company previously marketed a product that contained an ingredient known as 1,3 dimethylamylamine, or DMAA. In 2012, the Food and Drug Administration began sending warning letters to companies manufacturing DMAA-containing products demanding that they remove these products from the shelves. More recently, the Department of Defense issued a report on a safety review of DMAA after a number of adverse events and two deaths were reported in military service members who reported taking supplements containing the ingredient. In its statement, USPlabs said that the DMAA-containing version of its products has not been marketed or distributed since early in the year.

Regardless of the cause, hepatitis is a serious condition. The liver is the primary filter for toxins in the body, and hepatitis - which is essentially inflammation of the liver - shuts it down. Symptoms include yellowing skin and eyes and abdominal pain.

For now, both the CDC and FDA are investigating whether there could be more cases of this hepatitis in the mainland U.S.

Park said she is concerned that there could be. And she said that she feels the government shutdown could complicate the matter of catching them early. "Standard disease surveillance is not set up for this," Park said. "Since this is not an infectious disease, the investigation is much tougher."

Dr. Natalie Stavas contributed to this story.