By Susan Heavey and Lisa Richwine

WASHINGTON (Reuters) - U.S. health officials said Monday they had new evidence linking a contaminant to deaths and allergic reactions in patients who took the blood-thinner heparin, rejecting assertions by Chinese officials that the chemical was not to blame.

The U.S. Food and Drug Administration said new data from animal and other studies showed the contaminant -- over-sulfated chondroitin sulfate -- could trigger side effects like those now reported in the deaths of 81 heparin patients.

"That doesn't tell us everything, or the whole story, but it establishes a link," said Janet Woodcock, director of the FDA's Center for Drug Evaluation and Research.

Baxter International Inc in February recalled most of its heparin products, made with ingredients from China.

It was the latest in a string of recalls linked to China, ranging from contaminated pet food to excessive lead in paint that saw millions of toys swept from store shelves last year.

But Chinese officials said on Monday they had tested batches of heparin used by patient who reported health problems and only some of these batches contained the contaminant.

"The over-sulfated chondroitin can therefore not be the suspected root cause of heparin ADE (adverse events)," said Jin Shaohong, deputy director-general of the China National Institute for the Control of Pharmaceutical and Biological Products.

Speaking to reporters at the Chinese Embassy in Washington, Jin said he and other officials planned to visit Baxter's plant in New Jersey and expected Baxter's cooperation.