XI'AN, Nov. 20  -- Let's face it, some Chinese food can be addictive; maybe it's just the great taste, maybe it's the opium.

The owner of a noodle bar in Baoji City of northwest China's Shaanxi Province has been arrested on suspicion of adding the dried pericarp of ripe fruit from the opium poppy to his hotpot and noodles.

In late September the local food and drug administration collected samples of seasonings from Xiaomenghua Noodle Restaurant for routine tests. Opium was detected in both seasonings and chili oil.

Adding poppy seeds containing morphine to food is obviously prohibited by law, but some small restaurants and snack bars still add it to their dishes to keep customers coming back for more. A number of such cases have come to light in recent months and authorities have raised their levels of vigilance.

Also in September, a man was detained by police after a tip-off that he had stolen crude oil. He then tested positive for drugs, but his aunt suggested that the result might be due to a bowl of noodles. Investigation showed that the noodles were indeed opiated and the restaurant owner was promptly detained by the police.

Chinese hotpot, renowned for the "numbing and spicy" taste derived from pink Sichuan peppercorns frequently contains opium poppy seeds.

In early November, food inspectors in east China's Jiangxi Province seized 740 grams of poppy seeds from a hotpot restaurant in Nanchang City, and discovered papaverine -- an antispasmodic opiate -- in its hotpot soup base.

Such "secret recipes" are often used by small restaurants and snack bars, said a cook from a hotpot restaurant in southwest China's Sichuan Province.

"In order to cover up their illegal behavior, vendors grind the seeds and add the powder to ajino-moto (monosodium glutamate) or put it in a sauce used by customers as a condiment rather than in the soup base, which is easily detected by inspectors," he said.

Opium poppy seeds can be found in many markets or even on the Internet.

One shop in a small town in southern Sichuan, sells a "spice" -- poppy seeds -- that can help restaurants lure more customers.

"It sells well. You need to order it one week in advance, and we only sell it to people we know," the shop owner said.

The poppy capsule - the complete seed head - of "good quality" costs 400 yuan (about 65 U.S. dollars) per kilogram. Many hotpot restaurants buy it from her, the woman said.

An online shop "Jubaotang Herbs" even boasts "wholesale poppy capsule" on its homepage with a picture of hotpot beside it. The cheapest product costs 540 yuan per kilogram. According to the website, the products are shipped from Kunming, capital of Yunnan Province, which borders on the notorious Golden Triangle where narcotics production and trafficking are commonplace.

Although poppy capsules contain only a small amount of alkaloid, long-term consumption will lead to addiction, damage to the nervous system and induce chronic intoxication, said Zhao Lan, a doctor with the Third People's Hospital in Chengdu, capital of Sichuan.

Back in 2008, the poppy capsule was listed as "inedible material" and banned from food. Transporting, buying, selling, storing, or using small amounts of poppy capsule can lead to detention for up to 15 days, and a fine of up to 3,000 yuan.