ON a rumbling train from Kunming, Yunnan Province, to Shanghai, a middle-aged railway policeman in a blue uniform walks through the narrow aisles of crowded hard-seat carriages, eyes scanning every passenger's face and luggage.

He stops at a woman, probably a poor migrant, who's restless and shifts in her seat.

"Hand it over," commands the cop in a voice that can be heard all around.

The woman is silent, turns pale, shivers and sweats.

The policeman takes her to the attendants' room, summons a female attendant and leaves. A few minutes later the attendant comes out with several small plastic packets of white powder the woman had hidden in her vagina.

This happened a few months back, but it's not an unusual case for legendary anti-drug hero Wang Zaiming, a Shanghai Railway policeman.

Wang, 53, already having the title of the National Good People's Policeman -recently was honored for his work and gave tips to other railway police drug spotters. These law-enforcers will be saluted for UN Anti-Drug Day on Friday.

Wang has been with the railway system for 30 years, joining the war on drugs in 1997. His record of nabbing drug mules and other traffickers is impressive.

From 1997 to 2008 Wang uncovered 162 drug trafficking cases, arrested 181 drug dealers and traffickers, and seized 24.8 kilograms of heroin and 951 grams of ice (crystal methamphetamine hydrochloride).

On the same day that he nabbed the female mule, he also caught five men who had hidden heroin packets in their anus. Altogether, he confiscated around 700 grams of drugs on that day.

In the first six months of this year, Shanghai Railway police uncovered 364 drug trafficking cases, smashed six drug rings, captured 386 drug dealers, and seized 2,264 grams of heroin and 5,404 grams of ice.

Comparison figures for 2008 were not available.

These days, Wang says he's not as busy but that doesn't mean the problem has gone away. Instead of one train a day running from Kunming, Yunnan Province, to Shanghai in the past, now there are five, each making multiple stops. And traffickers are also using cars, buses, trucks, airline travel and finding ingenious ways to conceal contraband.

Wang is known for sharp eyes and uncanny intuition.

Since the 1980s, the railway line between Kunming and Shanghai has been a major trafficking route for heroin from the Golden Triangle in Southeast Asia.

"Preventing drugs entering through the city through this railway conduit is an important part of keeping drugs out of China," says Wang.

He usually nabs around 15 smugglers a month; his record was seizing 11 traffickers on a single Shanghai-bound train.

"We dare not relax our vigilance," says Wang. "The smugglers keep improving their ways of concealment and we have to keep up."

Wang looks for red flags, signs of a guilty conscience. They include little baggage for long-distance travel, nervousness, fidgeting, feigned sleep and alcohol consumption.

"But we cannot just walk up to a suspicious person and ask him or her to open luggage," says Wang. "If our search fails to turn up anything illegal, we have legal liability."

So Wang and other cops usually do not take action until they are quite sure they have the right person, after careful observation.

And when they are certain, they use the excuse of checking for flammable or explosive substances in suspicious baggage.

In some cases, targeted passengers have threatened to lodge a complaint if Wang opens luggage or checks their person.

"I'm even surer in these cases, and I always tell them that if I find nothing in my search, then they can write down my badge number and lodge a complaint," says Wang.

He says he has never been wrong.

Born in 1956 in Shanghai, Wang joined the army when he was 18, was demobilized three years later and became a Shanghai Railway policeman.

Even back then he was the scourge of thieves and usually captured around 50 every year.

In 1997, he was appointed to the anti-drug police force on the Kunming-Shanghai line.

He had never seen drugs before. All he knew was that heroin came as white powder, easily concealed, and that drugs trafficking was dangerous and sometimes fatal.

He learned on the job, fast. After a month he made his first seizure on a Shanghai-bound train.

He spotted a couple entering the platform from a side door, not the main entrance, which was unusual. They carried only a backpack and a gift package of coffee from Yunnan Province. Traveling suspiciously light for a very long trip. The train attendant confirmed there was no other baggage.

At night Wang found them lying in berths in carriage No. 12. He checked every hour and found them tossing and turning.

Duty and pride

Though he was quite certain about their being smugglers, he waited until 8am lest he disturb other passengers. In the morning he and another policeman challenged them, checking for flammable and dangerous substances. He asked to see their identification cards and backpack.

There was nothing in the knapsack but the gift package of two coffee tins was strangely heavy. Wang opened them and discovered 1,000 grams of heroin wrapped in plastic - his first drug bust.

Since then he discovered drugs in many hiding places, including radios, cookware, vacuum bottles and brassieres.

Then in early 1998 the smugglers seemed to disappear and he didn't catch anyone for two months. He knew something was going on. Kunming police told him smugglers were hiding drugs in body cavities or even swallowing packets.

Wang is said to have uncovered one of the first such cases on the railway - two men who swallowed heroin packets. Their pale faces and purple lips gave them away.

Wang is known to drug smugglers and he says there is a 200,000-yuan (US$29,259) contract out for his life. He narrowly escaped an assassination attempt on the train platform in Kunming in 1999.

Wang seldom smokes cigarettes given to him on the train, as they might contain drugs or poison.

"It is risky to be an anti-drug cop and you don't have much family time," says Wang. "But it's my duty and pride whenever I put on my cap with the national emblem on it. I swear I will never fail."