5 Held in San Gabriel Valley Robberies : Crime: Authorities arrested 18 suspected ‘Black Dragon’ gang members. But 13 were released for lack of evidence in more than 30 crimes.

Authorities on Thursday announced that they had taken into custody 18 suspected members of the “Black Dragon” gang, a loosely knit group of mostly young Southeast Asian refugees who are thought to be responsible for more than 30 armed robberies in the immigrant communities of the San Gabriel Valley.

Because many of their alleged victims have been reluctant to come forward, however, 13 of the suspects were released for lack of evidence shortly after their arrest Tuesday by a task force made up of officers from seven Los Angeles County law enforcement agencies.

Sheriff Sherman Block, whose department heads the North Regional Surveillance and Apprehension Team, asked for the Asian community’s help in identifying the suspects and tying them to more crimes.

Black Dragon’s “whole existence is based upon a very real understanding of the Asian culture, which is to accept victimization and keep quiet,” Block said. “We need those victims to come forward.”

Of the five suspects who were not released, four were charged with robbery and kidnaping in connection with a heist Tuesday at The Beauty of Paris Salon in San Gabriel, officers said. They are Thuan Kso Ngo, 29, Anthony Lenh, 19, Ty Pham, 22, and Vang Tram. The fifth suspect, Hong Ly, 21, was charged with armed robbery in connection with a Los Angeles holdup.

Block said the other 13 were arrested at what he called the gang’s “crash pad” in Rosemead.

Detectives said the Black Dragon is made up of about 40 youths, most of whom are the children of poor refugee families from Vietnam. They have been operating here since the mid-1980s and are suspected of contributing to the sharp increase of residential robberies in the San Gabriel Valley.

Unlike burglaries, in which thieves break in while a home is empty, a residential robbery depends on the occupants being there to show where valuables are kept, officers said.

Block said the gang succeeds because the victims are often fearful of retaliation, unfamiliar with the U.S. legal system or may not be documented residents of this country. He said officers were not interested in the victims’ background, but are seeking help in solving the crimes.

“The Asian victim is least likely to come forward and report their victimization,” Block said. “That’s that kind of thing we’re trying to break through.”