Chinese officials voiced doubts Monday that a contaminant identified in the blood thinner heparin was the root cause of severe allergic reactions in hundreds of Americans.

The officials suggested at an embassy news conference that the problem with the drug could have occurred in the United States. They plan to visit a Baxter International plant in Cherry Hill, N.J., to get a better picture of how the finished product is manufactured.

"When you see it, then you believe it," said Jin Shaohong, the deputy director general for the National Institute for the Control of Pharmaceutical and Biological Products in China.

Raw heparin is derived from pig intestines, often processed by small, unregistered workshops in China. The raw ingredient for Baxter's recalled heparin came from Wisconsin-based Scientific Protein Laboratories, which in turn owns a Chinese factory — Changzhou SPL — and buys additional raw heparin from other Chinese suppliers.

The Food and Drug Administration has counted 62 deaths from allergic-style reactions that were associated with recalled heparin batches. The FDA can't say for sure what caused the reactions, but the chief suspect is a contaminant that the agency discovered in supplies of raw heparin coming from China — a compound derived from animal cartilage that so closely mimics heparin that routine purity tests can't detect it.

Germany also discovered the contaminant and recalled batches of heparin after some patient illnesses.

But the Chinese officials contended Monday that batches not containing the contaminant — called oversulfated chondroitin — also have been associated with side effects.

"The oversulfated chondroitin can therefore not be a suspected root cause of heparin adverse events as reported in U.S. media previously," Shaohong said.

The FDA did not immediately respond, but Baxter denied that claim.

"We do not agree with that," said Baxter spokeswoman Erin Gardiner. "We have seen adverse event reports on batches where the contaminant has been confirmed to be present."

Baxter was considering the Chinese officials' request for additional heparin samples for their own further testing, Gardiner said.

The Chinese officials also said that aside from the U.S. and Germany, more than 10 other countries used heparin containing the contaminant to produce their final injection but reported no side effects. The officials also noted that the implicated Chinese factory — Changzhou SPL — was managed and overseen by a manager from its U.S. headquarters.