Drugs produced at a GlaxoSmithKline pharmaceutical plant in North Carolina closed earlier this week are safe, the company said, adding that production is due to restart by the beginning of next week.

The plant at Zebulon east of Raleigh manufactures inhaled medications. It was closed after routine testing found Legionella bacteria in two external cooling towers. "No employees are sick and no products have been compromised," a GSK spokesperson said. "Medicines were not exposed to the bacteria."

North Carolina health officials said no cases of Legionnaires' disease linked to the Glaxo plant have been reported. But GSK said the building was closed because the cooling towers maintain temperature and humidity needed for manufacturing and working conditions.

The US Food and Drug Administration was still looking into the incident on Thursday.