Cadila Healthcare Ltd said it received a warning from U.S. health regulators for violating manufacturing standards at two production sites in India, sending its shares down 17 percent to its biggest single-day percentage fall.
The letter from the U.S. Food and Drug Administration cites issues at Cadila's plants in the western state of Gujarat: the Moraiya drug production site and another in Ahmedabad city where it makes drug ingredients.
The warning for Moraiya comes more than a year after the FDA inspected the plant in Sept. 2014, and issued a report highlighting a series of problems. Cadila said in October its work to fix the issues was complete.
But it has not received U.S. approvals for drugs made at the plant for a year, causing it to miss the launch of a key drug, Asacol HD, in November.
On Thursday, Cadila said in a statement that it was "committed to resolve all the issues and revamp our quality systems and processes as the top most priority."
It was not immediately clear how much the Moraiya site contributes to Cadila's sales, but analysts have said getting the plant back on track is key for the company.
Cadila said none of its products being sold in the United States used any raw materials made at the Ahmedabad plant.
Cadila's shares were down about 15 percent at 0527 GMT in Mumbai, after earlier hitting their lowest intraday level since March.