Government workers wearing white coats and masks and equipped with tanks of carbon dioxide fanned out through remote chicken farms today, launching a dramatic and highly visible attempt to stop the spread of an avian flu virus by eradicating Hong Kong's chicken population.

More than 250,000 chickens were killed with carbon dioxide gas in the first day of an operation that involved thousands of government workers from a half-dozen agencies as well as private vendors, who also slit the throats of the birds and dropped the carcasses into plastic garbage bags. Yellow dump trucks and earth-moving machines made huge piles of poultry remains at three large landfills.

Meanwhile, despite assurances that the so-called bird flu cannot be contracted by eating chicken, Hong Kong restaurants were dropping chicken and poultry dishes from their menus and touting beef and pork as substitutes. "You can still see it on the menu," said the white-haired old man behind the cashier's desk at Hong Kong's famous Luk Yu Tea House restaurant. "But anything with two feet, we don't have."

So massive is the job that the government did not have enough salaried workers and ended up hiring day laborers to kill chicken and geese for one Hong Kong dollar -- the equivalent of about 12 cents -- per slaughtered bird.

Since the mysterious bird flu virus, called A H5N1, surfaced in May, it has infected at least 13 and likely as many as 20 people, four of whom have died. The Atlanta-based Centers for Disease Control and Prevention has said that poultry workers with prolonged exposure to infected chickens are most at risk of contracting the disease. But so far, children, mostly toddlers, make up the majority of those who have fallen ill.

The virus, which originated in birds but inexplicably jumped to humans, has caused widespread fears of a global flu pandemic. Hong Kong residents have largely stopped buying and eating chicken, causing poultry sales to plummet. Some tourists have stayed away. The new Chinese-appointed Hong Kong government, in power only six months, has been under intense public pressure to take steps to allay rising concern that the bird flu could spread out of control.

In an unusual front-page commentary, the English-language South China Morning Post newspaper said the wholesale slaughter of chickens was "the most dramatic gesture the authorities could make."

But the commentary added, "Unfortunately, radical move or not, the extermination of all Hong Kong's chickens only addresses one side of this equation." The main problem, it said, was that "the central question surrounding the spread of bird flu still has not been answered: Where does it come from? Until we know the answer, the killing of more than a million birds cannot hope to quell the public's understandable fears."

Late this evening, the task force involving three government departments -- urban services, agriculture and fisheries, and the regional council -- said more than 250,000 chickens and other poultry had been destroyed. The operation was to continue until the last bird is destroyed.

The government has said that all of Hong Kong's 1.3 million chickens -- as well as geese, quail, ducks and pigeons that may have been housed near chickens -- will be slaughtered within a day and a half.

Many vendors began slaughtering their own birds before the operation officially began. Blood oozed across the slick floors of empty stalls. The next phase of the operation will involve a massive cleaning of all the markets and stalls, in an attempt to eradicate the virus once and for all.

The slaughter of Hong Kong's live poultry population means that Hong Kong residents will have to get used to a drastic change in their eating habits. Chicken -- shredded, steamed, baked, roasted, served with chili, cashews, oyster sauce or soy sauce, and sometimes with names like General Tso's chicken or beggar's chicken -- has long been a staple on most restaurant menus.

Hong Kong residents like their chicken fresh, and several restaurateurs interviewed here said they preferred to remove chicken dishes from their menus than to lower their standards by using frozen birds from the United States or Australia.

"We would never use frozen food," said an indignant worker at the Luk Yu Tea House, which has counted among its guests cuisine-loving German Chancellor Helmut Kohl. The worker, who asked to be identified only as John, said, "If we use frozen foods, the taste is no good."

The Luk Yu lists more than 30 chicken and pigeon dishes on its menu, none of which was available today and perhaps for a long time to come. In addition to slaughtering all chickens in the territory, authorities have slapped a ban on live chickens coming in from southern China.

"Now that everybody is afraid of chicken, they are trying other types of food," John said.

Health experts have said there is no danger of contracting bird flu by eating chicken, but they advise that poultry be well-cooked.

With chicken sales near zero, most vendors seemed to welcome the slaughter. Some had complained earlier that they could no longer afford to keep the birds. The government has promised to compensate owners, and today began working on emergency legislation that would pay the equivalent of $3.85 for each destroyed bird.

While health officials and scientists have called birds the main source of the deadly influenza, they have not ruled out the possibility of human-to-human transmission.

Researchers believe that if the virus can travel from person to person, it does so inefficiently. Margaret Chan, Hong Kong's director of health, has said that H5N1 is not thought to be an airborne virus, and she has speculated that a health-care worker who fell ill with bird flu may have gotten it from contact with an infected patient's bodily secretions. Bird flu symptoms are similar to other strains of flu -- fever, chills, sore throat and muscle aches. But because this is a new strain of influenza, the general population has no resistance to it, making it a more serious health threat.

However, researchers who performed blood tests on more than 500 poultry and laboratory workers and people who had contact with flu victims, discovered that nine of them had developed antibodies to the virus. This suggested that some people have been exposed to the virus without becoming ill. CAPTION: Health workers carry rat traps into Hong Kong's Cheung Sha Wan chicken market, fearing rodents may carry the "bird flu" virus. CAPTION: Masked government workers collect poultry at a Hong Kong farm in a massive drive to kill the territory's estimated 1.3 million chickens. The eradication effort is designed to stem the spread of "bird flu," which has killed four people.