Sun Pharma, India's biggest drug-maker, on Saturday said that the US drug regulator has issued a warning letter to the company regarding violation of manufacturing norms at its Halol plant in Gujarat.

The US Food and Drug Administration (USFDA) had conducted inspections at the Sun Pharma's Halol facility in September 2014.

"Sun Pharma will respond to this Warning Letter with a detailed plan within the stipulated timeframe," the company said in a statement.

The letter by the USFDA indicated the company is "still months away" from receiving an approval for the plant by the agency. The regulator may impose a ban on all the drugs exported by the plant to the US if it fails to resolve the issues at the plant, Reuters reported.

The US drug watchdog has withheld approvals for products manufactured at the facility since the inspection in September 2014, which has affected Sun Pharma's sales in its largest market, the US.

"Post the September 2014 inspection, the USFDA has withheld future product approvals from the Halol facility. This situation may continue until all issues are resolved," it said.

Sun Pharma said that it would request for a re-inspection by USFDA after fulfilling its "remediation commitments."

"While our team is working hard to ensure that the commitments made to the USFDA in September 2014 are fully completed, we will continue to cooperate with the USFDA and undertake any additional steps necessary to ensure that the US agency is completely satisfied with our remediation of the Halol facility," PTI quoted Sun Pharma Managing Director Dilip Shanghvi as saying.

Over the past year, the US regulator has issued warning letters to a significant number of Indian pharma companies, as it increasingly monitored the manufacturing plants located in other countries.