A contaminated blood thinner from China suspected in dozens of U.S. deaths has become a worldwide public health problem, with 10 other countries detecting the often-toxic ingredient, federal investigators said Monday.

The compound, which in tests mimics the real blood thinner heparin but which costs less to make, may have been added deliberately somewhere along a production chain that began on farms in China, beyond the reach of U.S. regulators.

Food and Drug Administration officials issued a warning letter Monday that banned future U.S. shipments from the plant in China that supplied the widely used blood thinner until the safety issues are resolved. And officials raised the possible death toll from 62 to 81.