The suspected links between the Xing Da and the Chinese mafia have cast a spotlight on the country's secret criminal societies, or triads.

Washington State Department spokeswoman Susan Snyder said Xing Da was the 11th or 12th Chinese ship carrying illegal immigrants to be intercepted since 1991.

And she claimed the mafia charged the Xing Da 's passengers between $20,000 and $30,000 for the illicit passage.

According to the Federal Bureau of Investigation, the migration of triad members to the US is well-documented.

They can be found in street gangs, such as Ghost Shadows, Flying Dragons, Wah Ching, United Bamboo and Ping On.

But, say the FBI, there is no concrete information indicating triad organisations exist as direct entities in the US.

The word "triad'' is an English term derived from the Chinese criminal societies' sacred emblem -- a triangle whose sides represent three basic powers: heaven, earth and man.

Originally formed as resistance groups to the Ching Dynasty that ruled China from the early 17th century until 1912, triads continued to flourish in Hong Kong and Taiwan throughout the 1950s and 1960s.

They even controlled many important Police posts in Hong Kong until the early 1970s.

Today's triads are based roughly on models and traditions from the past.

The initiation ceremony of the triads is described in an article by Linda L.

Keene, an FBI special agent in Washington, which appeared in the FBI Law Enforcement Bulletin in 1989.

The article on Asian Organised Crime said the ceremony, known as "hanging the blue lantern'', required recruits to repeat 36 oaths of loyalty, secrecy and brotherhood.

"The integrity of the organisation's secrets is also strictly and brutally enforced by the triad's `Red Pole', an individual trained in the martial arts who, along with other henchmen, is charged with the responsibility of internal and external security.

"Triads still heavily rely on fear within the organisation, among competitive criminal groups and within the community.

"The practice of dispatching `hitmen' internationally to reinforce this fear is not uncommon.'' The origin, evolution, rituals, practices and modern activities of the triads are said to be remark ably similar to those of the Sicilian Mafia.

In Sicily, loyalty and solidarity are recognised by "omerta'', commonly known as the code of silence.

"Similar initiation rites are also present in both organisations, including the commingling of blood and the burning of paper,'' wrote Ms Keene.

"Last, aside from the fact that both the mafia and triads are engaged in criminal activity, they also have the ability to generate varying degrees of fear and respect among the general population.''