The government closed U.S. borders Tuesday to more than 30 generic drugs — including popular antibiotics and cholesterol medicines — made by India's biggest pharmaceutical company, citing poor quality in two of its factories.

The Food and Drug Administration's move doesn't end U.S. sales by Ranbaxy Laboratories Ltd. Instead, it blocks imports of generic drugs — including generic versions of the antibiotic Cipro and cholesterol pill Zocor — as well as pharmaceutical ingredients made at the two suspect plants in India.

FDA inspections earlier this year found violations that could lead to contamination, allergic reactions and other problems, and the company hasn't taken proper steps to correct them, said Deborah Autor, director of FDA's compliance office.

Also, the FDA said it won't approve any new products for sale by Ranbaxy until the manufacturing violations are corrected.

India has become one of the world's leading suppliers of generic drugs, and concern about Ranbaxy has been growing since FDA inspectors first uncovered quality problems at one of its factories in 2006.

Yet the FDA told consumers who have Ranbaxy products at home not to worry or quit using them: Repeated testing hasn't found any contaminated products, just the threat of them if factory conditions don't improve. Also, it would be hard for a patient to tell if drugs were made at the suspect factories or at one of Ranbaxy's numerous other factories in 11 countries.

"We have seen no evidence of harm to consumers from drugs produced at these two facilities and have no reason to believe that drugs already in the U.S. from these plants pose a safety problem," said FDA deputy drug director Dr. Douglas Throckmorton.

Among the blocked drugs: the antibiotics ciprofloxacin and clarithromycin; the antiviral acyclovir; cholesterol-lowering simvastatin and pravastatin; and the diabetes drug metformin.

The showdown is separate from a continuing criminal investigation of whether Ranbaxy submitted fraudulent data to the FDA that allowed sale of substandard drugs. Ranbaxy has vigorously denied that allegation, calling it part of a conspiracy to undermine the company. A call to Ranbaxy's U.S. headquarters Tuesday was not immediately returned.

The move also could affect a U.S. program that funds AIDS drugs for Africa, as Ranbaxy is one supplier of the low-cost generics being used. The FDA said it had notified charities and officials involved in the AIDS drug program of its concerns about drug quality.

The Ranbaxy warning comes amid mounting concern about the safety and effectiveness of imported drugs. A 2007 report found FDA inspectors haven't visited two-thirds of foreign drug manufacturers — and in July, members of Congress began probing whether the FDA knew that Ranbaxy had provided potentially fraudulent information but approved its products anyway.

"The FDA is not doing its best to protect the medicines that Americans depend on for their health," said Rep. John Dingell, D-Mich., whose House Energy and Commerce Committee is conducting that investigation.

The FDA said enough other generic companies make the blocked drugs that there should be no shortages, with one exception: Ranbaxy is the sole U.S. supplier of ganciclovir capsules, used to treat an eye infection called cytomegalovirus that is common in HIV patients. FDA will allow Ranbaxy to continue to import that drug under some special oversight until the manufacturing issues are resolved.

The factories with defects are in Dewas and Paonta Sahib, India.