The U.S. drug regulator has asked India's Ranbaxy Laboratories to immediately assess whether its plants making drugs for the U.S. market meet standards, the Economic Times newspaper reported on Friday.

Ranbaxy, India's top drugmaker which is majority owned by Japan's Daiichi Sankyo, in December said a U.S. unit had received a warning letter from the U.S. Food and Drug Administration (FDA) on violations of good manufacturing practices. A Ranbaxy spokesman said he had no fresh comment beyond that made in a statement issued on Dec. 24 in the wake of the FDA letter, where Ranbaxy said it would cooperate with regulators and remained committed to comply with standards.