That's what former Secret Societies Branch detectives Lionel De Souza, Lim Ah Soon and Theva told us.
The literature on the history of gangs also indicates that in the early 1760s, Tiandihui (literally, Heaven and Earth Society) was formed in China in the midst of the economic poverty and political instability then.
Many Han natives of China had banded themselves together to overthrow the Qing dynasty, which reigned in China from 1644 to 1911.
Later, the Tiandihui became known as the Three Dots Society, the Three Unities Society and the Hong League (or Hong Men).
The first secret society believed to have established itself in Singapore was the Ghee Hin Kongsi (formed here in 1820). The name means "the rise of righteousness" - an offshoot of Hong Men.
Many of the practices of early secret societies in Singapore were legitimate ways of helping Chinese immigrants to settle down here, such as searching for accommodation and employment.
But these groups devolved into crime syndicates, controlling brothels, gambling dens and the opium trade since the 1850s.
Banned during the 1890s by the British Government here, they survived, nonetheless, although most of them had become mere street gangs by the mid-20th century.
Today, most of the gangs in Singapore are believed to have originated from Hong Men, and they can be classified into "secret societies" and "triads".
Secret societies have no clear organisational structure and their members are recruited rampantly - often without much screening.
Triads, on the other hand, have a strict hierarchy and members must go through elaborate initiation ceremonies, often involving prayers.
In some rituals, the new members have to cut their fingers with a knife, drip their blood into rice wine and drink it as a sign of brotherhood.
It is believed that the only triads in Singapore today are the gangs that are of the lineage of "21".
Most of the other offshoots are secret societies.
The New Paper on Sunday spoke to four former police officers and eight former gang members to profile these gangs.
Their gang members operate mainly out of locations listed on the map (see right), but they are also known to move around due to recruitment or to facilitate vice activities.