GIRLS as young as 16 are among Vietnamese applying in unprecedented numbers to marry their way out of Hong Kong detention camps and into the homes of local Chinese, expatriates and refugees. Several women from the camps have even married their captors, officers with the Correctional Services Department (CSD), after overcoming the opposition of officialdom. Hundreds of Vietnamese women, most of whom have never seen Hong Kong except from within the confines of a detention camp, are every year becoming wives of usually older men in a social phenomenon which has brought joy and tragedy. On their wedding day, they are loaded like cattle into a steel cage covered by tarpaulins in the back of an unmarked government truck. The truck transports a group - set by a quota - from the camps to marriage registries at Sha Tin, San Po Kong and City Hall. Several are married simultaneously. After the service they are allowed to embrace their partner, relatives and friends and be photographed before being separated, sometimes forcibly, herded back onto the truck and returned to the camps. A CSD officer at a service attended by the South China Morning Post last week told a young Vietnamese bride moments after the ceremony: ''Don't go far away. Just take two photos. Otherwise, I'll handcuff you.'' Marriage notices show that cooks, cleaners, farmers, fishermen, technicians, construction workers, hairdressers, mechanics, photographers and electricians are among Hong Kong Chinese residents who have wed Vietnamese girls as young as 16 in the past two months. The boom in Vietnamese marriages has prompted the Whitehead Detention Centre to rent complete silk and lace wedding costumes and jewellery for a fee of about $1,000 for a few hours. In the past year, about 375 Vietnamese women migrants from the High Island, Whitehead, Chi Ma Wan and Nei Kwu Chau detention camps have wed people outside the camps, according to the CSD. There were 295 such unions in 1992. Most Vietnamese migrants face a tough initiation into married life because of communication problems, a cultural chasm and bad experiences in the camps, according to couples who have been through it, camp workers and marriage counsellors. ''Since she doesn't know Cantonese, we will avoid many arguments,'' said Poon Shu-chi, 34, a watch technician who last week wed Tran Thi Thuy, 13 years his junior, in a service at Sha Tin. ''I hope I can live with my wife as soon as possible,'' he said as she was urged back on the CSD truck with four other brides and driven away. But it can take as long as two years after a Vietnamese migrant tells her camp welfare officer that she wants to get married before she is allowed out of the camp and into her husband's home. Marriage applications by Vietnamese migrants have become so common that it can take one year before they are allowed to wed. At Whitehead Detention Centre, Hong Kong's largest camp for Vietnamese, an average of five applications are lodged every day by migrants, most of whom would otherwise be sent back to Vietnam. ''It takes quite a long time for them to be married because too many Vietnamese migrants are applying now,'' a source said. The sheer volume of cases has forced the CSD and the Immigration Department to regulate the marriages by determining a weekly quota, causing a massive backlog, the source said. On average about 10 a week are taken by truck from Whitehead for civil services at the nearby Sha Tin Marriage Registry, which has been stretched to full capacity. After the Vietnamese are married it can take a month to a year before they are allowed out of the camps and united with their spouses in Hong Kong and countries including the United States, Canada and the United Kingdom. The agonising delay has contributed to the breakup of several marriages before the partners have been united, according to one social welfare worker. ''This is the hardest part. We are deeply in love. We're married, we know she's coming out, but we don't know when,'' said a newly wed expatriate, whose Vietnamese wife has been detained in the camps for more than five years. He said he recently dissuaded a woman who was facing forcible return to Vietnam from marrying a Vietnamese drug addict with a criminal record who had refugee status and could offer her the same. ''That's how desperate a lot of them are. None of them want to go back to Vietnam.'' A senior officer in the Immigration Department said there was a backlog of more than 300 cases of newly-wed Vietnamese migrants waiting to have applications for Hong Kong and overseas residency approved. If a Vietnamese marries a foreigner and seeks overseas residency the cases are referred by the Immigration Department to the relevant consulate in Hong Kong for determination. ''Some are waiting over one year. It takes time for consulates to respond because each has its own criteria,'' the officer said. Although the Hong Kong Government and some foreign governments suspect that many of the marriages are shams so that migrants can avoid being sent back to Vietnam, conclusive evidence has been difficult to obtain. ''We have reason to believe that a number of marriages in Hong Kong camps have taken place for immigration reasons,'' said Government Refugee Co-Ordinator Brian Bresnihan. ''Getting married is a basic human right. There is no question of the Hong Kong Government stepping in to stop marriages unless there is a legal impediment, such as one or both of them already being married.'' An Immigration Department spokesman said officers conducted investigations into all cases involving Vietnamese migrant applications for Hong Kong residency after marriage - and prosecuted bogus ones. ''They are free to marry. Whether or not they are allowed to stay in Hong Kong or to depart for overseas resettlement depends on their ability to satisfy the principle of family unity and prospect of being accepted by a third country,'' he said. ''How do these women meet their husbands? This is a very important question we have to ask. We have to find out their dating patterns. They should have a course of meetings and very frequent contact. We have to assess all of this.''