One in 10 of the inspections carried out at construction sites last year found mosquitoes breeding there.
That is out of some 12,000 inspections that were carried out last year, said Environment and Water Resources Minister Vivian Balakrishnan, in response to MPs' queries in Parliament on the dengue situation.
Contractors have been penalised with fines that total $3.5 million, he said.
In the last six months, the Government has issued 55 stop-work orders and prosecuted 26 contractors in court, Dr Balakrishnan added, urging construction contractors to strengthen the environmental management at worksites.
Last year, dengue cases peaked at 842 a week in June, while for the week of March 2 to 8, there were 210 reported cases of dengue fever here.
Dr Balakrishnan said the current outbreak is driven by a new strain of the dengue Type 1 virus, which accounts for up to 85 per cent of all diagnosed dengue cases, as the population has low herd immunity against this strain.
Meanwhile, he added, the National Environment Agency is deploying new tools like gravitraps which catch mosquitoes and their eggs, allowing officers to monitor where dengue-carrying Aedes mosquitoes are spreading.