China’s drug safety agency says it enforces strict controls on chemicals used in pharmaceuticals, but that importing countries are ultimately responsible for ensuring product safety, the Associated Press reports.

The State Food and Drug Administration, in a statement on its Web site, says it is cooperating with a US probe into a factory that makes Heparin, a blood thinner sold by Baxter International that is subject to a massive recall due to some 350 adverse patient reactions and four deaths.

“We attach high importance to this,” the agency said in its first comment on the Heparin recall. SFDA officials have not responded to repeated inquiries about the case. But the SFDA says that, based on international practice, “safeguarding the legality, safety and quality of raw materials imported for use in pharmaceuticals is the responsibility of the importing country.”

Earlier this month, Baxter recalled thousands of vials of the blood thinner and halted production, although the cause of the adverse reactions remains unclear. The US FDA is conducting inspections at a Baxter facility in New Jersey; at Scientific Protein Laboratories in Wisconsin, which supplies Baxter with ingredients; and at Changzhou SPL, a factory in the eastern Chinese city of Changzhou that is 55 percent owned by Scientific Protein.

China’s SFDA said it also was investigating the factory, but gave no details. The heparin scare is the first big issue to arise since Washington and Beijing signed an agreement in December that was meant to improve coordination on food and drug safety following a spate of scandals over tainted or substandard products. FDA officials say cooperation has improved.

But the case highlights the difficulties both sides face in improving oversight given paltry levels of staffing and funding on both sides. The FDA acknowledged that Changzhou SPL was never inspected by the FDA, contrary to its own regulations, due to what it says was a mix-up with names. The Chinese FDA apparently did not inspect the factory because it was classified as a chemicals manufacturer, not a pharmaceuticals company.