The U.S. Centers for Disease Control and Prevention has closed down its highest security laboratories after discovering that hoses that supply air to scientists wearing special protective suits were never approved for that use, the agency said on Friday.

"We have no evidence that anybody has suffered ill health effects from breathing air that came through these hoses," Stephan Monroe, associate director for laboratory science and safety at the CDC, told Reuters.

Monroe said he was confident that scientists were not exposed to pathogens because the air they breathed passed through HEPA filters. The suits they wear also use positive air pressure to prevent pathogens from entering the suit.

Monroe was named to the newly created position in 2015 in response to a months-long internal investigation into the mishandling of anthrax, bird flu and Ebola in CDC labs in 2014.

CDC is now conducting safety tests to determine whether the scientists might have been exposed to harmful chemicals that passed through the air hoses.

The problem stems from the original construction in 2005 of the Biosafety Level-4 laboratories, in which scientists handle the most dangerous biological agents.

The air hoses are part of the building's infrastructure. They drop down from different ports within the lab, and scientists plug the hoses into their suits from different work stations.

CDC officials learned about the problem earlier this week when they were ordering replacement hoses, and were told by the manufacturer that they were not certified for breathing air. Monroe declined to name the company.

He said the CDC routinely tests the air quality in the tank that feeds the hoses to ensure it meets standards set by the Occupational Safety and Health Administration.

"We've been testing the air in the tank. Not the air as it comes out of the hose," he said.

CDC will now test air from the old tubing to check for any toxic chemicals, but Monroe said there is no evidence that breathing air from the hoses caused any ill effects. CDC notified people who have been using the air hoses earlier this week.

The agency has ordered replacement tubing that is expected to be installed this weekend and plans to bring the labs back online next week.

(Reporting by Dipika Jain in Bengaluru; editing by Maju Samuel)