Those infected include 36 foreign construction workers employed at a site near Aljunied in the southeast of the island, the health ministry and the National Environment Agency (NEA) said in a joint statement on Sunday.
On Saturday, authorities had confirmed Singapore's firstcase of a local transmission of the virus, to a 47-year-oldMalaysian woman, also from the Aljunied area.
"MOH (the ministry of health) cannot rule out further community transmission in Singapore since some of those testedpositive also live or work in other parts of Singapore," thestatement said. "We expect to identify more positive cases."
The authorities said they have tested 124 people, primarily construction workers. Seventy-eight tested negative and fivecases were pending. Thirty-four patients have fully recovered.It was not immediately clear where the foreign workers werefrom, but Singapore hosts a large contingent of workers from theAsian sub-continent.
"All the cases are residents or workers in the Aljunied Crescent/Sims Drive area. They are not known to have travelledto Zika-affected areas recently, and are thus likely to have been infected in Singapore. This confirms that localtransmission of Zika virus infection has taken place," the statement said.
Dozens of NEA staff cleaned drains and sprayed insecticide in the mainly residential area early on Sunday, and volunteersand contractors handed out leaflets and insect repellent. The NEA workers had accessed more than 1,800 premises of a total of6,000 in the area to check for mosquito breeding.
Local residents welcomed the clean-up.
"I'm very scared of mosquitoes because they always seem tobite me, they never bite my husband," Janice, 31, who gave onlyher first name, told Reuters. "This concerns me because maybe ina couple of years I want to have another (child)."
Zika was detected in Brazil last year and has since spreadacross the Americas. The virus poses a risk to pregnant womenbecause it can cause severe birth defects. It has been linked tomore than 1,600 cases of microcephaly in Brazil.
The Singapore government said there were "ongoing localtransmission" cases in Indonesia, Thailand and Vietnam. Othercountries in the region to have detected the Zika virus since2013 include Bangladesh, Cambodia, Laos, Malaysia, Maldives andthe Philippines, according to the World Health Organisation (WHO).
Malaysia said on Sunday it stepped up surveillance at maintransit points with Singapore.
Health director-general Noor Hisham Abdullah said leafletson Zika prevention were being handed out and paramedics were atentry points to handle visitors with potential symptoms.
As of this month, Malaysia said it has screened more than 2million visitors at air, sea and land entrances, and found noZika infections.
In Thailand, where close to 100 cases of Zika have been recorded across 10 provinces this year, the Department of Disease Control (DDC) was screening all athletes returning fromthe Olympic Games in Brazil, but was not otherwise changing its prevention measures.
"Every country in this region has Zika transmission cases,"said Prasert Thongcharoen, an adviser to the DDC. "Thailand has,however, managed to contain the problem through early detection."
Indonesian foreign ministry spokesman Armanatha Nasir saidthe country was "following developments". Oskar Pribadi, ahealth ministry official, said there have been no recent Zika cases.
Vietnam has to date reported three cases oflocally-transmitted Zika infection.
The current strain of Zika that is sweeping through Latin America and the Caribbean originated in Asia, where people couldhave built up greater immunity.
US health officials have concluded that Zika infections inpregnant women can cause microcephaly, a birth defect marked bysmall head size that can lead to severe developmental problems.
The WHO has said there is strong scientific consensus that Zika can also cause Guillain-Barre, a rare neurological syndrome that causes temporary paralysis in adults.//Reuters