This was the finding of the state health department in its random checks at construction sites in Selangor recently.

Aedes larvae were found in polystyrene containers left by workers, wheelbarrows and in puddles of water on the floors of unfinished buildings.

Larvae were also found in old tyres, rubber shoes, man-holes, drums, paint tins and construction helmets.

According to the department, this was one of the main factors contributing to the high number of dengue cases in Selangor last month.

Health director Dr Rosnah Hadis, in a recent report, said eight out of 10 sites inspected were found to be breeding ground for aedes mosquitoes.

"In fact, construction sites are the biggest obstacles to the health authorities' fight against dengue in Selangor," she said.

Last month, 4,389 cases of dengue were reported in Selangor, with areas in Shah Alam recording the highest number, at 332 cases.

Statistics revealed that Selangor, at one point, recorded an average of 19 people coming down with the fever daily.

Statistics also showed that of 154 construction sites inspected since early this year by the department, 103 were breeding grounds.

Last month alone, an immediate stop work order was slapped on 25 construction sites for failing to keep their areas free of aedes mosquitoes.

The department also issued compound summonses on five developers while another five were given stern warnings to clean up their areas or face stop-work orders as well.

Streets recently followed a team from the department in its visits to several construction sites and found out that some irresponsible contractors failed to keep their sites from becoming breeding grounds for mosquitoes.