NANING：In a detention house in south China's Guangxi Zhuang Autonomous Region, on the Vietnam border, Hai Li, 18, an illegal immigrant from Vietnam, represents her fellow townspeople as they communicate with the police.

In Vietnam, many young people want to work in China because the pay is much better, Hai says. "I earn 800 yuan a month here. Back home, I could only get 450 yuan at most."

Hai came to work at a cellphone shop in the southern Hainan Province two years ago and learnt to speak fluent Mandarin, even some Hainan dialect. She was caught by border police when returning to work after the Spring Festival vacation.

Hai and the others who came with her will be deported to Vietnam. But she says, "I will come back to China with a visa. My boss in Haikou City has promised to raise my wages."

Guangxi border police have seized 1,820 illegal immigrants, stopped 4,839 others from entering and deported 2,218 people since 2009, says a spokesman with Guangxi border police.

However, at least 10,000 illegal immigrants have come to Guangxi's Chongzuo City alone, says Mo Shaoren, deputy head of Chongzuo's human resources and social security department.

Large numbers of illegal immigrant workers from Vietnam had been found in factories and farmlands of south China cities. Most came through Guangxi's Dongxing and Pingxiang border cities, the police spokesman says.

Most local young men have gone to work in larger cities, leaving a shortfall of 30,000 farmers in normal times and 50,000 during busy seasons. Vietnamese nationals often come to fill the gaps, Mo says.

Vietnamese nationals are welcomed in Chongzuo, where they are seen as hard-working and cheap, accepting only half the wages of a Chinese worker.

A local worker can cost an employer 80 yuan a day while the Vietnamese are usually satisfied with 40 yuan a day, Mo says.

On Chongzuo City's 553 km border with Vietnam, only 260 border police are deployed, far from enough to curb the illegal immigration on 123 routes, says Li Zuozheng, chief of staff of Chongzuo's border police.

By March 20, Chongzuo's border police had stopped 420 illegal Vietnamese immigrants this year, of whom 175 were detained and investigated and 10 deported, Li says.

But no authority can tell the exact number of illegal immigrants from Vietnam working in the Pearl and Yangtze river deltas, he says.

The situation has worsened with the severe drought plaguing northern Vietnam, which has driven many farmers to seek work in China, said Fan Qi, head of Fangchenggang City's border police.

On a mountain road just 30 meters from China's official entry in Pingxiang City, groups of Vietnamese cross the border without any checks.

In just 10 minutes, 14 people in three groups came into China through the route while six people left carrying large bags of goods.

A spokesman with the regional police says a crackdown was launched in March to curb the immigration, with stricter identity checks and searches at customs and border check stations.

The border police of Fangchenggang City apprehended 56 illegal immigrants from Vietnam, as well as one Vietnamese and eight Chinese organizers on March 24, the spokesman said.

On April 4, the police seized 19 Vietnamese illegal immigrants in a railway station of regional capital Nanning City, he added.