The US Food and Drug Administration has recalled thousands of bottles of antidepressants because the drugs contained high levels of a cancer-causing chemical.

Now the FDA is assigning the second highest risk level to the recall of duloxetine extended-release capsules manufactured by Towa Pharmaceutical Europe.

The capsules have been classified as a Class II recall, “a situation in which use of or contact with a violating product may cause temporary or medically reversible adverse health effects, or in which the likelihood of serious adverse health effects is remote.”

Duloxetine is used to treat depression, anxiety, and nerve pain caused by fibromyalgia.

However, routine production checks detected small levels of a cancer-causing chemical called N-nitroso-duloxetine.

These chemicals are commonly found in water and food, but the FDA regulates how much of this chemical can be contained in certain items because the chemicals can be harmful in high concentrations.

The FDA is investigating the source of the drug’s impurities. In the meantime, the organization advises patients who have been prescribed these medications not to stop taking them until they have spoken to a healthcare professional about their concerns and may explore other treatment options.