The US Food and Drug Administration has recalled more than two million needles made by a Japanese firm over fears they can introduce silicone fragments in patients' bodies.

The FDA said in a statement Tuesday that Nipro Medical Corp. had taken back products made between January 2007 and August 2009 after inspections in October last year showed between 60 and 72 percent of the needles were defective.

The needles are used to access ports implanted under the skin of chronically ill patients so that blood can be withdrawn or medications infused repeatedly.

Testing showed that when the needles were inserted into the port they sometimes produced slivers or "cores" of silicone, which could be flushed into the patient's body with adverse results.

Although 20 manufacturers produce the needles, only those made by Nipro were found to frequently result in coring.

"We will continue to work with manufacturers to address coring issues as quickly and thoroughly as possible," said Jeffrey Shuren, director of the FDA's Center for Devices and Radiological Health.