BEIJING (AP) -- China's drug safety agency accused the United States on Tuesday of blocking Beijing's inquiry into a blood thinner linked to 81 deaths by refusing to provide details on victims and specifics about production.

Two Chinese experts who attended a conference on the drug, heparin, in suburban Washington, D.C., last month said the U.S. determined a contaminant was likely to blame without considering other possible factors.

''We need to resolve this in a scientific matter, not just by blaming a contaminant,'' said Jin Shaohong, a member of the drug evaluation committee of China's Food and Drug Administration. ''I think it is too early to say that.''

Besides the deaths, hundreds of patients have suffered severe allergic reactions to large doses of heparin, which is used in dialysis and other treatments.

The U.S. Food and Drug Administration said it suspects the problems stem from a contaminant the agency discovered in supplies of raw heparin coming from China -- a compound derived from animal cartilage that so closely mimics heparin that routine tests can't detect it.

The Chinese experts said U.S. officials and Deerfield, Ill.-based Baxter International refused to give them information to probe the possibility that drug interactions, patients' medical histories or safety issues after the raw material left China may have played a role.

FDA spokeswoman Karen Riley said Tuesday that she could not recall China asking for medical histories.

''We've not received a request from China about patient records,'' Riley said.

Li Xuewang, a professor at Peking Union Medical College who attended last month's conference, said he asked for information such as how many of the patients had medical issues like kidney disease or heart problems and was told it was not available and could take several months to provide.

Federal law prevents the FDA from sharing individual patient information that contains identifying information.

''Some of the level of detail that China is asking for would likely have to be removed to comply with our patient privacy laws,'' Riley said.

She added that when adverse events are reported, the patient records involved in those cases will be posted on the FDA's Web site with the personal detail withheld. She expected detail involving the Heparin cases to be posted in June.

Riley noted that individual case reports did not prompt the heparin investigation in the first place. Rather, it was clusters of reports coming in from providers, lawyers and relatives showing that patients were experiencing similar adverse reactions. A subsequent inquiry identified Baxter's heparin as the likely cause of the allergic reactions.

Members of the Chinese delegation also visited the Baxter plant in Cherry Hill, N.J., where the finished drug is made, but said they were denied details on how specific batches of the medicine were produced last fall.

Jin said Baxter International told the visitors that samples from the batches had either been taken by the FDA or destroyed.

Officials at Baxter International, the maker of heparin, disagreed.

''We've cooperated with all parties involved in the heparin situation and we will seek to understand any concerns to the contrary,'' said Erin Gardiner, a company spokeswoman.

She said Baxter had agreed to provide Chinese officials with contaminated heparin samples when they visited the New Jersey plant two weeks ago, but first needed to assure it had samples to spare. That has now been confirmed and samples will be provided, she said.

China has said the contaminant, over-sulfated chondroitin sulfate, may not be responsible because some patients who received the tainted heparin did not get sick. Other patients received doses that did not contain the contaminant but still became ill, officials said.

The investigation into heparin comes as China has been working to improve the safety of its exports after allegations that many of its products -- from toys to fish -- are shoddy or dangerous.