A gang of extortionists that for months has threatened to poison candy sold in Japanese stores has fulfilled its threat, touching off an intense police manhunt and emergency recall of the affected goods.

In the past two days, police have found 11 cyanide-laced packages of candy in 10 different stores in the Osaka-Nagoya area. They are now searching for others that bizarre letters signed "the 21-faced mystery man" or "21-faced monster" say have been planted.

There are many parallels to the Tylenol case in Chicago two years ago, where seven people died from cyanide-spiked capsules of Tylenol. But in Japan, where many criminals consider physical violence bad form, the specimens were neatly marked with a type-written note: "Poisoned. Danger. You will die if you eat this. The 21-faced mystery man."

No one ate any of the different kinds of sweets, which included cookies and chocolate-covered nuts, all products of one of Japan's largest candy companies, Morinaga & Co. But laboratory analysis showed that some of the candy did, in fact, contain enough cyanide to kill.

Today, the National Police Agency issued a highly unusual statement declaring that the crime "has created fear throughout society" and asked for public cooperation in apprehending the criminals. No arrests have been reported.

For months, the Japanese public had followed closely what was an often semicomic duel between another candy manufacturer and a shadowy criminal group, which at times seemed more concerned with publicity and posturing than money. Suddenly, it turned serious.

Japan is famous for its rock-bottom rate of violent crime. Nonetheless, the Japanese retain a lurid interest in crime and criminals. Newspapers give such heavy play to murders and kidnapings that do occur that the foreign visitor might conclude the country is peopled largely by miscreants.

Conventional wisdom holds that the candy poisoning is not the work of the yakuza, criminal groups that run such traditional underworld businesses as pornography, illegal betting and drug distribution. Generally, these people avoid publicity and concentrate on making money.

It began last March, when Katsuhisa Ezaki, president of a nationally known candy company, EzakiGlico, was kidnaped from his home near Osaka while taking a bath. Three days later, he turned up safe, saying he had escaped from his captors.

His troubles continued, however. First, his office was struck by arson. Then letters began arriving at the company and the media threatening to poison the candy, which was on shelves around Japan, unless 300 million yen (about $1.2 million) was paid immediately.

The letters, always typed, grew more elaborate. Their author took the name of "21-faced mystery man" after a master criminal in Japanese detective fiction, the "20-faced mystery man," who bamboozles the cops no matter how hard they try. Police psychologists have theorized that self-agrandizement was one of his main motivations.

No poison appeared but the public stopped buying the candy and retailers began shunning it. Company officials have estimated that by next spring, they will have incurred $12 million in lost sales. Market value of their stock also plunged.

Then in June, the gang announced in a letter to its "fans" that it had grown tired of the affair and was leaving for Europe for a rest.

Nothing more was heard from them during the summer, although police were kept busy with a spate of copycat extortion bids directed at a bakery, a pharmaceutical company and another candy firm. Arrests were made in all of them.

Then, in mid-September, a letter arrived at Morinaga & Co., demanding a payoff of 100 million yen (about $400,000) to forestall poisoning of its stock. Letters, addressed to "mothers all over the nation," went to the media warning of the danger.

"Twenty packages of candy, which we have specially seasoned and are slightly bitter with sodium cyanide" had been placed in stores, it said. After 10 days, 30 more would be introduced. On Sunday evening, a supermarket clerk found the first of them.

A reported 600 police have been assigned to the case full-time. Morinaga, meanwhile, has vowed it will not give in to extortion. But already its stock is slipping.

As happened in the Tylenol case, supermarkets are pulling all Morinaga products off the shelves.