There is no reason to believe that last Sunday's riot in Little India stemmed from unhappiness among foreign workers, Prime Minister Lee Hsien Loong said on Saturday.
"We have not seen any evidence of that," he said, when asked about speculation that pent-up tensions among foreign workers might have been a cause.
The riot was spontaneous and localised, with signs that alcohol was a factor, he said. It also involved men from many different companies and living in different places.
"It is unlikely that all the companies will have the same problem," he told reporters in Tokyo, where he attended a summit marking 40 years of ASEAN-Japan relations.
In the aftermath of the riot, Law and Foreign Minister K. Shanmugam visited foreign workers at their dormitories and spoke with them in the presence of the media.
"There is no tension, there is no sense of grievance or hardship or injustice," Mr Lee said.
About 400 men, mostly of South Asian origin, were involved in the riot after a traffic accident left a worker dead. So far, 33 men have been charged in court.
A large area around Little India has been declared a no-alcohol zone this weekend, and private buses that usually ferry foreign workers to and from the place on their day off will not run today.
The usually bustling area was noticeably quieter on Saturday, with an increased, visible police presence.
On Saturday, the police issued a brief statement in the evening saying it is illegal to organise or take part in a public assembly without a permit.