The workers were issued formal police advisories as their involvement in the riot was passive and incidental, the Channel News Asia reported.
The workers were accompanied by representatives of the companies they work for.
The police advisory said the workers must abide by Singapore's laws and if they commit any criminal offence, their work permit may be revoked.
The report said many workers and their representatives did not know why they had to be there.
"I had already checked with my worker. But he wasn't involved in anything. That's why I asked the police officer. The police officer didn't say anything," Suresh Babu, an administrative manager at a company in Singapore, was quoted as saying.
Heng Siak Hoe, owner of an outdoor spray painting unit, also accompanied his worker but said he did not know why police asked him to come.
The riots broke out after an Indian worker, Sakthivel Kumaravelu, died Dec 8 after being run over by a bus in the Little India area here.
Mobs attacked police officers who responded to the accident call in what was termed the biggest riot in Singapore in 40 years.
Fifty-seven foreign workers have so far been deported, majority of them Indians.
--IANS (Posted on 22-12-2013)