Novo Nordisk, a leading Danish manufacturer of insulin, has received a US subpoena requesting documents relating to potential manufacturing issues at its plant in Kalundborg in Denmark.
The Kalundborg factory 100km west of Copenhagen is the world's largest insulin production facility, as well as manufacturing enzymes, in addition to another non-insulin diabetes treatment known as GLP-1.
The company said the request had come from the office of the US Attorney for the District of Massachusetts, adding that it related to 'certain production units'.
Novo Nordisk said it did not have more specific details but was co-operating fully with the US Attorney in this investigation.
The company added: 'At this time, Novo Nordisk cannot determine or predict the outcome of this matter or assess the consequences thereof. In addition, the company cannot predict how long the investigation will take or when it will be able to provide additional information.
'Novo Nordisk takes patient safety and product quality very seriously and is confident in the safety of its products.'