Large quantities of heroin are moving out of Vietnam to China for the first time, in a sign of Hanoi's growing role as an international smuggling centre. Police and foreign diplomats are working for closer co-operation on the border to stop the trend, which has so far seen as many as 30 Vietnamese traffickers arrested in China. Traditionally, Vietnam's heroin has trickled in from China but the market has now become so flooded with the drug from other sources that traffickers have turned the country into a major exporter, police sources said. The new trade points to the success of routes - some assisted by senior Vietnamese police - bringing massive quantities of heroin from the Golden Triangle through Laos and into Vietnam by road. The mountainous province of Quang Ninh on Vietnam's northeastern coast is now seen as the hub for the new China trade, fuelled by a myriad of land and sea crossings. Traffickers have jumped on relaxed immigration rules at the Mong Cai border gate that allow as many as 1,500 traders to cross with day passes. Enforcement is weak and smuggling rampant but further relaxations are planned, with Mong Cai earmarked for eventual special economic zone status. Like Hanoi, the streets of Quang Ninh's villages and towns are awash with high-grade heroin cheaper than anywhere else in the world. The headmaster of one primary school has reportedly built a large wall around his classrooms to keep dealers, who spike candy and ice cream with the drug, at bay. 'The heroin situation is now so active and fluid in Vietnam that we are seeing the creation of entirely new routes and syndicates,' one source said. 'Unless firm action is taken now, these new players will be extremely hard to break down and could become major international players in the future.' The news comes ahead of the start this week of Vietnam's biggest-ever drug trial - a case which could see at least 27 people sentenced to death. Some 40 people will appear following the arrest of several senior federal police within Vietnam's powerful Interior Ministry for involvement in a ring that smuggled an estimated 300 kilograms of heroin to Hanoi. The arrests were sparked by a 'gallows confession' from a convicted Laotian trafficker about to face a Vietnamese firing squad. Sieng Pheng was given a reprieve by the Office of the President as sweeping internal investigations began, and is expected to appear in court under heavy police protection.