NEW YORK _ Koreans in the U.S. are typically known as hard-working and successful, but in some communities, they’re starting to pick up a new reputation for something different _ prostitution.

A series of large-scale Korean prostitution rings have been busted throughout the country recently, prompting authorities to target massage parlors specifically run by Koreans as a major source of sex trafficking.

Harris County, Texas, filed a petition earlier this week, demanding a forced shutdown of three spa businesses owned by Koreans.

The petition claims that these spas, which have become hotbeds of prostitution and human trafficking, hire young women _ mostly from Korea _ to perform services.

According to county officials, hundreds of concerned residents filed complaints to law enforcement agencies since 2009, which finally triggered a major undercover crackdown last month that saw the arrest of seven women.

``Found condoms, dark lit rooms, massage tables that are pushed up against the wall,’’ Sergeant T.E. Kiser of the Harris County Sheriff’s Office told local media.

The massage parlors were already busted a few times, but officers say the shops opened up again within days, which ultimately led to the request for a shutdown.

A similar clampdown in Federal Way, Washington in January led to the arrest of eight Koreans who operated a Korean-style ``room salon,’’ where men paid money for sex. The club owner allegedly recruited women from Korea to serve as bar girls and forced them to work as prostitutes.

``The organizers of this criminal scheme exploited vulnerable young women to satisfy their greed,’’ U.S. Attorney Jenny A. Durkan said in a statement. ``They also sought to protect their business by offering bribes to law enforcement.’’

On the other side of the coast, authorities in Duluth, Georgia, saw the problem with Korean spas as so severe that they decided to toughen the city ordinance that regulates massage parlors.

New York City, Los Angeles and San Francisco are among other cities that have been in the news in recent months for busting big-scale prostitution rings operated by Koreans, many of whom are illegal aliens.

``It’s embarrassing that Koreans are being outwardly associated with brothels and prostitution,” said Kim Tae-woong, an official of the Federation of Korean Associations, U.S.A.

``Korean immigrants have worked hard and long to build a certain image and reputation to this point,’’ he said, ``so it would be such a disgrace for these small few to ruin it for all of us.’’

But Koreans’ sex trafficking in the U.S. isn’t anything new.

According to the U.S. Attorney General in 2006, South Koreans accounted the highest population (24 percent) of sex trafficking victims in the U.S., followed by Thailand, Peru, Mexico and El Salvador.

Korean massage parlors, simply called KMPs among those in the know, have often carried a shady image, but things have got shadier over the past few years.

Observers say the start of the visa waiver program (VWP), which took effect in November 2008, has played a role in facilitating sex trafficking.

According to the U.S. Department of Homeland Security, 230,000 undocumented Koreans reside in the U.S. as of January 2011. This is up 60,000 from one year ago.

``We don’t know where all these people are, but I’ll bet many are working at places where they shouldn’t be,’’ says John Kim, an immigration lawyer practicing in New Jersey. ``There aren’t any hard numbers to prove anything now, but U.S. authorities are definitely taking into account the rise of all these illegal activities to assess the visa waiver system.’’