They hide for weeks cramped within the bleak metal walls of cargo ship containers, tossed by rough seas, trapped in total darkness and bound for American shores on desperate voyages that begin halfway around the world.

Stowaways smuggled from China through elaborate criminal networks are besieging the ports of the West Coast, turning up dazed, sick or dead on docks from here to Seattle. It is a sad spectacle growing worse every month, and federal officials say it may be difficult to stop.

Since Christmas, more than 50 Chinese nationals, nearly all young men, have been discovered in some of the thousands of cargo containers that freighters deliver to this giant port every day. Already this year, an additional 85 have been nabbed in containers on ships docked in Seattle and just across the border in Vancouver, including three who were found dead last week amid their own filth.

Ports in other parts of the Pacific Northwest, as well as Southern California, are reporting outbreaks of the same problem. In all, several hundred Chinese being smuggled to the United States and Canada have been caught in recent months virtually sealed in horrific conditions inside cargo containers the size of boxcars. And port authorities are sure that scores of others have managed to sneak unnoticed out of bustling shipyards.

"This is a huge smuggling operation we're up against," said Michael Fleming, an administrator for the branch of the U.S. Customs Service that oversees the neighboring ports of Long Beach and Los Angeles. "And it's getting harder to discover. There's no way we could look inside most of the containers that come off these ships every day."

It is an old story with a new twist: For decades, U.S. Coast Guard and Customs officials on the West Coast have regularly caught groups of young Chinese nationals trying to get smuggled into the country. Until recently, they usually have been fairly easy to spot. Most have been riding on ragged fishing vessels listing across the high seas, captured with ease, then deported back to China. Last spring, the Immigration and Naturalization Service sent home about 500 Chinese nationals who were discovered near Guam.

The crackdown on the seas has been so successful, federal officials say, that it is forcing smugglers to resort to far more extreme measures. "This is their reaction to what we've been doing," said Sharon Gavin, an INS spokeswoman. "The situation that they are putting these people in now is incredibly perilous."

In Seattle last week, port authorities acting on a tip found 18 Chinese men jammed inside a 40-foot metal cargo container with a canvas top. It had been their squalid home for weeks, with no light and little air because several other containers had been stacked on top during the long journey at sea. They had plastic buckets for human waste, a few flashlights and not much water. Three had been dead for days when dock workers ripped the box open. The others staggered out barefoot and were hospitalized.

Federal officials say that incident is the most wretched of their discoveries so far, but others have not been much better. Here in Long Beach last fall, authorities found 54 Chinese men, including some teenagers, who had spent three months at sea crammed inside two small and narrow cargo containers of a freighter.

Once captured, the men are telling the same grim tale: Most are from rural provinces on the southern coast of China and traveled from their peasant villages to Hong Kong with the hope of being smuggled to America on cargo ships, no matter how harsh the circumstances. The price of the trip is steep. Some smuggling networks demand up to $50,000 or more, money few of the men have.

Entire families of the men scrape together cash for down payments. Then, in exchange for passage to the United States, the stowaways become indentured servants, promising future wages from their work in sweatshops or other parts of the nation's underground economy. And they know full well that if they do not pay their debts, the lives of family members could be in danger. Federal investigators here also say that most of the men are bound for illegal factory work on the East Coast, primarily in New York.

"This is not a small-time, seat-of-the-pants smuggling operation," said Stanley Rosen, a professor at the University of Southern California who specializes in Chinese affairs. "It has a long history, and it's very sophisticated. There's also a lot of money involved, because running it well requires so many payoffs."

The sheer size and frenzied pace of ports along the West Coast can make catching the stashed human cargo akin to finding a needle in a haystack. Here in Long Beach, which is the biggest and busiest port in the nation, docks sprawl for 3,000 acres and churn all day with industrial bustle. About 5,000 ships, most coming from Asia, drop anchor and unload more than 4 million cargo containers a year. At Seattle's port, ships deliver about 1.5 million cargo containers a year. Most of the time, the smuggled men are found by chance.

Hiding on freighters that are 500 feet long and often have only two dozen crew members is not difficult, and ports say that at best they inspect about 10 percent of cargo containers as they are unloaded.

"We really don't know what's inside most of the containers," said Art Wong, a spokesman for the Port of Long Beach, "because until now we never had that much of a problem with people trying to smuggle human cargo like this." Most ports simply rely on shipping lines to provide lists of cargo contents.

But port officials are getting more aggressive. Some are walking dogs trained to detect human scents past rows of cargo containers. Investigators are also paying closer attention to the smaller percentage of canvas-topped containers--because smugglers hide many of the men in them--and keeping watch on the edge of shipyards for runners waiting to pick up the illegal immigrants. Two men arrested on Jan. 2 while waiting in a van at Seattle's port were indicted Thursday on charges of attempting to smuggle a dozen Chinese nationals from cargo ship containers into the country, at a cost of $60,000 each.

Federal authorities also say that government officials in Hong Kong are helping with their investigations and vowing to start using heat sensors on many cargo boxes before they are loaded on ships.

In Canada, where the smuggling problem in western ports is also severe, Customs officials are imposing stiff penalties on ships found with illicit human cargo. One ship that docked in Vancouver Jan. 4 with 25 Chinese nationals on board was fined $375,000. Last fall, after finding 54 people stashed on a cargo ship in Long Beach, U.S. officials charged its captain and crew with assisting in the smuggling, a felony. They could face a $250,000 fine and as much as 10 years in prison. But imposing sanctions on crews or shipping lines for having smuggled humans aboard is still uncommon in the United States.

Federal officials say they do not believe that most shipping companies, or their seafaring crews, are usually even aware they have illegal immigrants on board. "At this point we're trying to emphasize cooperation with them," said INS spokeswoman Gavin. "Maybe they can help us with this problem."

In some instances, smugglers, or "snakeheads" as they are known in China, have sought to provide some comforts to the stowaways during their frightful trips across the Pacific. Port investigators have found fans, mattresses, even cell phones inside a few cargo containers. But most of the time, they see what they saw last week in Seattle: frail men sharing scraps of food and water, in a box fast becoming a tomb.

"It's brutal," Fleming said, "and stopping it will be a formidable task."

CAPTION: Chinese immigrants huddle next to container filled with malnourished and dehydrated stowaways Jan. 10 in Seattle.