The U.S. Food and Drug Administration sent a letter to Mylan Pharmaceuticals — the manufacturer of the EpiPen — on April 3 detailing quality control issues at one of the company's facilities in India.
The letter, publicly released on Tuesday, outlined violations at the facility pertaining to the employee invalidation of 101 out of 139 quality control tests conducted from Jan. 1, 2016, to June 30, 2016, which suggested drug batches failed to meet quality standards.
"Your investigation did not reach an assignable cause, nor did you take appropriate corrective actions and preventive actions to ensure that the significant 'analytical bias' to which you ultimately attributed the initial failure would not affect other analytical work in your laboratory," wrote the FDA in the letter. "Your quality system does not adequately ensure the accuracy and integrity of data to support the safety, effectiveness, and quality of the drugs you manufacture."
After news of the letter broke Tuesday, the drug manufacturer's stock took a 2 percent hit, according to CNBC.
"Mylan received a warning letter with two observations from the U.S. Food and Drug Administration and we are working closely with FDA to respond to and address the issues raised in the letter as comprehensively and expeditiously as possible," said a Mylan spokeswoman in a statement to CNBC.
Production is currently uninterrupted at the facility, which produces antiretroviral drug therapies for the treatment of HIV, according to CNBC.
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