Multiple lots of weight-loss medication Wegovy were recalled by pharmaceutical giant Novo Nordisk because hair was found in a prefilled syringe, according to two notices published by the Food and Drug Administration (FDA) this week.

The recall entails lots of four Wegovy, or semaglutide, single-dose prefilled pens in 0.5 mg/0.5 mL doses, according to an FDA notice issued on Dec. 31. The other notice, published on the same day, said that four Wegovy single-dose prefilled pens at 1 mg/0.5 mL doses are also under recall.

The recall is due to the “presence of particulate matter” in which “hair was found in a prefilled syringe,” the notices say.

The company voluntarily initiated the recall and sent a letter, according to the FDA. The notices did not say how many units or lots of the drug are under recall.

In a statement last month, Novo Nordisk said that two pen injectors that had particulate matter “were caught during inspection and were never sent out to the retail level or patients.”

“There are no confirmed reports of this issue in any Wegovy pens that are already on the market and no adverse effects known to be related to this issue have been reported from product in these lots to date,” the company said. “No action from patients is needed or recommended at this time and any potential medical risk would most likely be minor.”

It added that “patient safety is our top priority, and we are committed to ensuring that all of our products are of the highest quality.”

“We will work closely with the FDA and other stakeholders to ensure an appropriate process is in place related to these four batches so that the recall is handled safely and promptly,” the company said, while saying there is no impact to the supply of Wegovy due to the recall.

Both recalls were classified by the FDA as Class II on Dec. 31, which the agency defines as “a situation in which use of or exposure to a violative product may cause temporary or medically reversible adverse health consequences or where the probability of serious adverse health consequences is remote.” Class II is the second-highest in a three-tiered classification system under the FDA.

Shares of Novo Nordisk, the maker of Wegovy and the popular weight-loss drug Ozempic, were up by more than 1 percentage point by midday trading on Friday. The company’s shares received a significant boost last week after the FDA granted approval to the company’s Wegovy weight loss pill.

Wegovy is a popular prescription drug that’s designed for weight loss in adults who are overweight or obese, or who have related conditions such as type 2 diabetes, high blood pressure, or high cholesterol.