According to Ah Xiang, foreign laborers are becoming increasingly popular in factories in the east, as domestic workers are thin on the ground, while foreigners tend to be cheaper, more "well-behaved" and "quiet."

But the opportunities to make more money in China are often outweighed by terrible working and living conditions, Ah Xiang added, pointing out that it is hard to guarantee the rights of the illegal workers.

Experts attribute the phenomenon to a wide range of factors, including rising labor costs in China as well as loose supervision.

One of the underlying reasons for the rampant black market in foreign labor is that China's coastal cities have come under pressure from a severe shortfall in labor resources, according to Yu Yimao, captain of Baise's border control police.

In February, a survey by the Guangzhou Human Resource Market Service Center showed a shortfall of 123,300 workers in Guangzhou, capital city of Guangdong. A similar warning was issued later by the Fujian provincial government, cautioning that the province needs 80,000 laborers to fill the gap.

Meanwhile, the cost of domestic labor is on the rise.

Construction worker Li Deqin said that the daily salary for people like him used to be about 80 yuan ($13), but now they command at least 180 yuan.

That is a huge contrast to many foreign workers like Mi Lenh, who barely makes 50 yuan each day in Vietnam.

"I heard that even stowaways can make more than 100 yuan a day in China," the young Vietnamese said.

While his dreams have now become castles in the air, many others are still falling for the bait, and authorities have called for a taming of the black market with a spate of proposed legal measures.

Xu Ningning, deputy secretary-general of the China-ASEAN Business Council, said that China needs to ramp up supervision to tackle the problem, for that is in the interest of both foreign workers and domestic factories.

"I think that the government could work with the Association of Southeast Asian Nations to figure out a mechanism to ease the labor pressure and guarantee the rights of workers," Xu said.

He suggested that the problem could be solved by qualifying and legalizing more foreign laborers to work in China under government supervision.

Global hunt for top skills accelerates	Illegal foreign worker expelled