The charge:

Having paid for sex with an underage girl.

Prostitution is allowed in Singapore, but having paid sex with a person under 18 is illegal; the laws were tightened in 2008.

Who:

Forty-eight men, including public servants. The accused, aged 21 to 48, include a former police superintendent, military officers, a laywer, businessmen, people in finance and other professions.

Former Pei Chun Public School principal Lee Lip Hong, 39, emerged as the only one to plead guilty. His case will come up on April 27.

Most recently, former Singapore Environment Council executive director Howard Shaw and a former top banker have emerged among four more men to be charged on Wednesday.

The online vice ring:

The girl's services were touted on a website allegedly run by Tang Boon Thiew, who owns an online marketing firm.

He was charged in November 2011 with running the online vice ring and also faces one count of paying the girl for sex.