The crowd ran as police officers swarmed around them, blocking every exit out of the alley.
In a raid on Wednesday night at Geylang, 15 of them were arrested for illegal gambling and drug offences in the area.
But 15 minutes after the authorities left the scene, it was business as usual with the illegal gambling tables set up once again, reported Chinese newspaper Shin Min Daily News.
An unnamed 54-year-old gambler told Shin Min that he was at a back alley in Geylang at about 8pm on Wednesday to "try his luck" at an illegal gambling stall.
Suddenly, a huge number of police officers in plainclothes appeared at both ends of the alley.
He added that some members among the crowd of gamblers also revealed themselves to be police officers.
"I tried running out of the back alley and some tried running to a nearby coffee shop but there were police officers already stationed everywhere," he told Shin Min.
The gambler and about 70 to 80 others were then rounded up for questioning, he said.
Shin Min reported that the questioning lasted till about 11.15pm, before police took the 15 arrested suspects away in two police vehicles.
Officers were also reportedly seen packing confiscated items into four to five boxes.
But soon after the police left the scene, the illegal gambling stalls between Lorong 16 Geylang and Lorong 18 Geylang were reportedly reopened, with gamblers continuing to try their luck at games.
A police spokesman told The New Paper that 14 men, aged between 17 and 58, and a 32-year-old woman were arrested for illegal gambling and drug offences.
The operation was reportedly the third consecutive raid on these illegal gambling stalls conducted this week.
On Monday and Tuesday, at least 14 others were already nabbed for similar offences, reported Shin Min.
A 42-year-old chef, who wanted to be known only as Mr Yang, told the evening daily that the operations were carried out swiftly without much noise.
Police investigations are ongoing.
This article was first published on October 9, 2015.
Get The New Paper for more stories.