During a visit to a facility of leading drugmaker Ranbaxy Laboratories Ltd last year, US inspectors found that a black fibre embedded in a tablet may have been a hair from an employee's arm, according to documents seen by Reuters.
That and other quality concerns led the US Food and Drug Administration to impose an "import alert" on its Mohali plant last week, saying the factory owned by India's biggest drugmaker by sales had not ensured manufacturing quality.
Ranbaxy, which is 63.5 per cent-owned by Japan's Daiichi Sankyo Co and gets more than 40 per cent of its sales from the United States, did not immediately respond to a request on Wednesday for comment on the FDA observations.
The FDA's action has dealt another blow to an Indian generic drug industry battered by a rash of American regulatory rebukes and as U.S. demand for generics grows, especially under President Barack Obama's new healthcare programme.
The import alert issued to Ranbaxy prohibits it from making FDA-regulated drugs at the Mohali facility and selling them in the United States until its methods, facilities and controls are in compliance with good manufacturing standards.
The unexpected import ban on the Mohali facility sent shares in Ranbaxy plunging by one-third on Monday, and comes just a few months after it pleaded guilty to U.S. felony charges related to drug safety and agreed to $500 million in fines.
It brings under sanction all three of Ranbaxy's plants in India dedicated to supplying the United States, and followed FDA inspections in September and December last year.
During one of the inspections, the FDA concluded that a black fibre embedded in a tablet was likely either "tape remnants on the nozzle head of the machine or a hair from an employee's arm that could be exposed on loading the machine", the documents showed.
Ranbaxy had said on Tuesday it would review the details of the FDA import alert and take "all necessary steps to resolve the concerns" at the earliest.
"The USFDA had conducted inspections at Ranbaxy's Mohali facility in 2012, resulting in certain observations," Ranbaxy said in the statement. "The company believes that it has made further improvements at its Mohali facility ... and remains committed to addressing all concerns of the USFDA."
The Mohali plant, in the northern state