Shares of drug firm Dr Reddy’s Laboratories today plunged 14.5 per cent after the company said it has received a warning letter from the US health regulator over inadequate quality control procedures at its three drug manufacturing units in India.

The stock took a severe beating and tumbled 14.49 per cent to Rs 3,636 on BSE.

It plummeted 14.52 per cent to Rs 3,632 on NSE.

The stock was the biggest loser on both the Sensex and the Nifty.

The letter was issued by the United States Food and Drug Administration (USFDA) yesterday for its three manufacturing plants at Srikakulam, Miryalaguda and Duvvada, the company said in a BSE filing.

“Dr Reddy’s Laboratories today issued a statement acknowledging that it has received a warning letter issued by USFDA dated November 5, 2015, relating to API manufacturing facilities at Srikakulam, Andhra Pradesh, and Miryalaguda, Telangana, as well as oncology formulation manufacturing facility at Duvvada, Visakhapatnam, Andhra Pradesh,” the filing said.

This action follows earlier inspections of these sites by the agency, it added.