The agency is withholding a list of Chinese heparin suppliers requested by congressional investigators looking into problems with tainted supplies of the blood thinner, saying confidentiality agreements prevent release of the names, The Wall Street Journal reports.

Members of Congress also are concerned that Chinese heparin manufacturers and their raw-material suppliers didn’t fully cooperate with an FDA inspection team in February, after the heparin crisis erupted internationally, and barred the FDA from complete access to some workshops, records and workers, the paper writes.

An FDA compliance official testified to a congressional subcommittee April 29 that the FDA could try to revisit facilities in China, but said, “I cannot say whether they will admit us or not, or whether they will allow us to do a full inspection.”

Tensions between congressional Democrats and the FDA over the agency’s handling of the heparin problem and its willingness to disclose info have escalated in recent weeks. “The FDA thinks they have it under control, but they really don’t,” Bart Stupak, a Michigan Democrat who is leading the investigation, tells the Journal.

He adds that FDA reluctance to release the names of Chinese companies is a red flag. “If I was the FDA director, I’d shut down every drug coming in from China” until they were deemed safe.

An FDA spokeswoman tells the paper that the agency is looking at finding a way to give the committee the info it requested 10 days ago without violating confidentiality agreements involving proprietary info.

Stupak’s House subcommittee is investigating the circumstances surrounding at least 81 US deaths linked to tainted Heparin derived from Chinese raw materials. The FDA doesn’t yet know how or when the contaminated ingredient, oversulfated chondroitin sulfate, was put into the supply, but agency officials believe it was likely a deliberate act, possibly to stretch the supply of a profitable export, the Journal notes.

Most of the reported problems have involved Heparin USP, given in large doses intravenously during heart surgery and kidney dialysis to prevent clotting. In February, FDA inspectors were allowed to inspect the Changzhou SPL plant that made the main heparin ingredient for Baxter International, then the largest US maker of Heparin USP, the paper writes.

But in recent testimony, an FDA inspector said Chinese manufacturers barred them from complete access to two of Changzhou’s consolidators of crude heparin supplies. Changzhou is majority owned by Scientific Protein Laboratories of Wisconsin. A Baxter spokeswoman, Erin Gardiner, tells the Journal that Baxter “is seeking access further down the supply chain to the Chinese facilities” that feed Changzhou SPL.

The Chinese government, meanwhile, has insisted that its products didn’t cause American deaths and that Baxter wasn’t cooperating in China’s investigation. “We disagree,” Gardiner says. “We hosted the Chinese in April at our plant in New Jersey and have agreed to provide them with heparin samples.”

The FDA is relying on voluntary testing agreements with some companies to check their Heparin ingredients for contamination before they distribute their supplies in the US, an FDA spokeswoman tells the paper, citing congressional testimony by FDA officials. The FDA didn’t issue a blanket “import alert” legally holding up all Chinese heparin pending successful testing, because it doesn’t have the legal authority to do so, FDA officials have said.

The tainted Heparin scare has become one of several cases congressional Democrats have used to criticize the Bush administration, the Journal points out.

Janet Woodcock, the FDA’s drug safety director, has said agency actions involving Chinese imports are limited by a Memorandum of Agreement with China. That agreement helped speed the entry of the FDA to China and helped open lines of communication with Chinese regulators, an FDA official testified. But Stupak called the memorandum “useless,” he tells the Journal, adding that, “I can go to the plant there and look at the paint on the walls, but not be allowed to inspect the lab.”