WASHINGTON (AP) — Medical device maker Baxter International said Tuesday federal regulators have given the company's recall of dialysis machines the most urgent safety warning available.

The Deerfield, Ill.-based company issued a recall on certain HomeChoice dialysis machines in January after reports of patients overfilling their abdominal cavities.

The company said the Food and Drug Administration has categorized the action as a Class I recall, its most severe level. The classification applies to problems that can cause "serious adverse health consequences or death."

Baxter said it is still investigating the source of the problems and is working on changes to labeling and software to prevent patient errors.

The company stressed that the machines do not need to be physically returned to the company and can still be used.

Patients and caregivers are advised to watch out for signs of abdominal overflow such as: difficulty breathing, vomiting or spitting up.

Baxter said it has received serious injury reports and at least one patient death report associated with the issue over the last two years.