WASHINGTON — The tainted pet food scare, which has swelled into a serious crisis for animal lovers, now has spread to humans.

California officials have revealed that the contamination got into the food chain: About 45 state residents ate pork from hogs that consumed animal feed laced with melamine from China. Melamine is used to make plastics, but it also artificially boosts the protein level — and thus the price — of the glutens that go into food.

It was already fatal for some pets: 17 cats and dogs are confirmed dead, more have likely died without being reported, thousands have suffered kidney problems, and 57 brands of cat food and 83 of dog food have been recalled. On top of that, roughly 6,000 hogs will be destroyed because they ate tainted feed. The effects of melamine on people are thought to be minimal, but no one really knows. Its consumption by humans is considered so improbable that no one has even studied it.

But they are studying now. What last month was a limited recall of canned pet food is on the verge of becoming a full-fledged public health scare, potentially overwhelming government agencies and raising troubling questions about U.S. food safety in the global economy and in the post-Sept. 11 era.

The Food and Drug Administration, criticized by some in Congress for responding too slowly, is struggling to catch up with the implications of the spread of melamine-contaminated glutens from China to hogs, and the human food chain. The FDA is still trying to get its investigators into China, where a skeptical government only last week assented to investigators' visa requests.

At a time when food imports are growing, and only 1 percent to 2 percent of food imports receive any government scrutiny, critics say the outbreak reveals the shortcomings of a weakened food safety bureaucracy, the inadequacy of existing regulations and the inability of the FDA, which has suffered significant cutbacks, to protect the food supply.

"They're reactive, not proactive," said Rep. Bart Stupak, D-Mich., whose House subcommittee on investigations last week held a hearing on food safety. If the problem was imported pet food additives, he asked, "How does it then get to hogs? They've known about this for some time. What did they do with it?"

In a statement, the FDA said that "food safety funding" for the year ending last Sept. 30 "was $376 million." But funding for the agency's Center for Food Safety has dropped from $48 million in 2003 to about $30 million in 2006, according to the center's 2006 budget priority statement. Full-time jobs in the Center for Food Safety have also been cut from 950 in 2003 to about 820 in 2006, according to the budget statement.