Last week, The New York Times asked the F.D.A. whether the Shanghai Pharmaceutical Group exported to the United States any drugs or pharmaceutical ingredients other than the abortion pill. But after repeated requests, the agency declined to provide that information; it did not cite a reason.

Image Liu Kechen, 29, who also became paralyzed after injections with the contaminated drugs in a Beijing hospital, receives help from his wife, Ma Jingrong, in stretching his legs. Credit... Du Bin for The New York Times

On at least two occasions in 2002, Shanghai Hualian had shipments of drugs stopped at the United States border, F.D.A. records show. One shipment was an unapproved antibiotic and the other a diuretic that had “false or misleading labeling.” Records also show that another unit of Shanghai Pharmaceutical Group has filed papers declaring its intention to sell at least five active pharmaceutical ingredients to manufacturers for sale in the United States.

One major pharmaceutical company, Pfizer, declined to buy drug ingredients from Shanghai Pharmaceutical Group because of quality-related issues, said Christopher Loder, a Pfizer spokesman. In 2006, Pfizer agreed to evaluate Shanghai Pharmaceutical Group’s “capabilities” as an ingredient supplier, but so far the company “has not met the standards required by Pfizer,” Mr. Loder said in a statement.

Because of opposition from the anti-abortion movement, the F.D.A. has never publicly identified the maker of the abortion pill for the American market. The pill was first manufactured in France, and since its approval by the F.D.A. in 2000 it has been distributed in the United States by Danco Laboratories. Danco, which does not list a street address on its Web site, did not return two telephone calls seeking comment.

Problems with the cancer drugs first surfaced last summer after leukemia patients received injections of one cancer drug, methotrexate. Afterward, patients experienced leg pain and, in some cases, paralysis. At the People’s Liberation Army No. 307 Hospital in Beijing, a 26-year-old patient, Miao Yuguang, was unable to stand up five days after being injected in the spine with the drug. “We were already unlucky to have this illness,” her father, Miao Futian, said of the leukemia. “Then we ran into this fake drug.”

The authorities recalled two batches of the drug, but issued only mild warnings because the cause of the problem was unclear. Officials with Shanghai Pharmaceutical Group stood by their products, saying that drug regulators investigating the plant had found no problems. But when another cancer drug made in the same factory  cytarabin hydrochloride  also began causing adverse reactions, investigators suspected contamination.

In September, health and drug officials announced that they had found that the two drugs were contaminated with vincristine sulfate, a third cancer drug, during production. After issuing a nationwide alert, the government announced a wider recall, and Shanghai’s drug agency sealed manufacturing units at the plant.