Industrial shops, such as the ones at Tampines Industrial Park A, are for industrial use and are not to be converted into a workers' dormitory, a Housing Board (HDB) spokesman told The New Paper.
"HDB is investigating the suspected misuse of the industrial premises at Tampines Industrial Park A and will take appropriate action, if there is evidence that the units had been misused," he said.
He said that cases of misuse are not easily detected by HDB officers, especially for places which are not open in the day.
"We will conduct night inspections and look out for tell-tale signs such as (the) presence of beds to assess whether they are misused as workers' quarters."
Larger factories can use part of their premises for housing workers, but they must meet various safety, hygiene and environmental requirements, according to HDB's website.
The Manpower Ministry (MOM) rules also state that these have to be checked by various statutory boards.
For example, they must meet fire and safety standards by the Singapore Civil Defence Force, building safety standards by the Building and
Construction Authority, and proper sanitary and drainage standards by national water agency PUB.
The MOM website said that employers who do not ensure that their foreign workers have acceptable accommodation can be prosecuted under the Employment of Foreign Manpower Act.
If a company is unable to meet these requirements, the Ministry will reconsider all of its future applications or renewal of work passes.
Companies must also register and update the addresses of all their work permit holders.
Employers found guilty of failing to provide acceptable accommodation can be fined up to $10,000, and/or jailed for up to a year.
Two migrant worker advocacy groups said they have received complaints from workers about their living conditions at unlicensed dormitories.
Mr Bernard Menon, executive director of the Migrant Workers' Centre (MWC), said: "The complaints usually concern overcrowding, unsanitary (and) unsafe conditions, lack of personal and storage space, (and) not enough toilets or wash facilities, amongst other things."
Mr Jolovan Wham, executive director of Humanitarian Organisation for Migration Economics (Home), said he does not know how many, out of the nearly 800,000 non-domestic foreign work permit holders here, live in illegal dormitories.
"What we do know is that there are 200,000 purpose-built dorm spaces. The rest are living in factory-converted premises, private apartments, shophouses, HDB (flats) and on construction sites," he said.
This article was first published on December 27, 2014. Get The New Paper for more stories.