Singapore (AFP) - Singapore on Sunday confirmed 41 locally transmitted cases of the Zika virus, which can cause deformities in unborn babies, and said more infections are likely.

A day after announcing its first locally transmitted case, that of a 47-year-old Malaysian woman resident, the government reported 40 more -- mostly foreign workers at a construction site.

All 41 are residents or workers in a particular suburban residential and industrial district, the Ministry of Health and the National Environment Agency said in a joint statement.

"They are not known to have travelled to Zika-affected areas recently, and are thus likely to have been infected in Singapore," the statement said.

"This confirms that local transmission of Zika virus infection has taken place."

It said that at this point the community transmission of the virus appears to be localised within the Aljunied Crescent and Sims Drive area, which hosts high-rise residential blocs and some industries.

However, since Zika is spread by the Aedes mosquito -- which also carries the dengue virus -- the health ministry "cannot rule out further community transmission... since some of those tested positive also live or work in other parts of Singapore", the statement said.

The health ministry said it has alerted clinics and hospitals to be "extra vigilant" and report patients with symptoms associated with the virus, mainly fever and rash.

Health Minister Gan Kim Yong told local media more imported cases are likely because Singapore is an international travel hub.

And because many Zika carriers display only mild symptoms or no symptoms at all -- meaning infected people may not seek treatment -- local transmission of these imported cases "is also very high", he said.

Health officials said the current infections came to light after a local clinic on August 22 reported an unusual rise in viral fever.

This prompted a check by health ministry experts, who told doctors to refer new cases to the government-run Communicable Diseases Centre.

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The National Environment Agency has deployed more than 200 officers to inspect and destroy possible mosquito breeding sites in the area.

According to the statement, 36 of the 41 cases involve foreign labourers working at a construction site in the area.

Work was halted at the site on Saturday after an inspection by environment agency officers discovered that housekeeping was "unsatisfactory with potential breeding habitats favourable to mosquito breeding", the statement added.

Twelve on-site workers' quarters and two other dormitories elsewhere were also inspected and one breeding site was detected and destroyed.

Singapore hosts thousands of foreign construction workers, most of them from South Asia.

The statement said 34 of the total number infected have fully recovered while the other seven, who are still symptomatic and potentially infectious, remain in hospital.

The latest outbreak of the disease began in Brazil in early 2015.

Singapore in May reported its first imported Zika case, a 48-year-old male Singapore resident who had travelled to Sao Paulo in Brazil earlier in the year.

In the United States more than 2,500 people have been diagnosed with Zika, most of them infected while travelling abroad.

Zika causes only mild symptoms for most people, such as fever and a rash.

But in pregnant women, it can cause microcephaly, a deformation in which babies are born with abnormally small brains and heads.

The Singapore joint statement urged pregnant women to monitor their health and seek medical attention if they are unwell.