Federal safety regulators have launched an investigation into whether Fresenius Medical Care hid the deadly side effects associated with its dialysis solution called GranuFlo. Use of GranuFlo has been linked to a significant increase in heart attacks and deaths in patients that have undergone dialysis. The New York Times reports that patients receiving GranuFlo were up to six times more likely to suffer from heart attacks than other patients.

An internal memo indicates that employees at Fresenius knew that its GranuFlo solution was causing heart attacks. The internal memo calls the GranuFlo-linked deaths “troubling” and adds that “this issue needs to be addressed urgently.”

Reports indicate that Fresenius executives failed to warn dialysis patients of the risks associated with GranuFlo. This failure seems to be entirely motivated by profit and the company’s fear that it would face defective dialysis product litigation and wrongful death lawsuits.

Fresenius Medical Care is the largest provider of dialysis services and products in the world. Fresenius operates dialysis centers throughout the country and reportedly provides services to 150,000 individuals across the country. In addition to providing dialysis products in its own clinics, Fresenius also sells dialysis solutions and products to other clinics and competitors.

Investigators from the Food and Drug Administration (FDA) believe that Fresenius became aware of the link between GranuFlo and heart attacks in 2010, but only warned physicians in its own clinics of the problem.

“Personally, I’m troubled by the fact that Fresenius on its own initiative didn’t notify its entire customer base of this particular concern,” said Steven Silverman, an FDA director of compliance. “Candidly, I just think it’s bad business and not in the interest of public health to sit on information about risks.”

It is unclear how many dialysis patients died as a result of Fresenius Medical Care’s failure to warn of the risks associated with GranuFlo. The dangerous dialysis solution is still being used and marketed to non-Fresenius operated clinics, and the company is attempting to get a FDA approval for a new dialysis solution that does not contain sodium diacetate, the substance linked to the heart attack risks.