JOHOR BARU • Most chemical factories in Pasir Gudang have committed offences under the Environment Quality Act, according to State Health, Culture and Heritage Committee chairman Mohd Khuzzan Abu Bakar.

He said out of 90 factories inspected by the authorities, 81 were found to have committed at least one offence under the Act.

"The Department of Environment has issued 71 compounds, four notices and six warnings to them to cease operations. The inspection is ongoing," he told a press conference on Tuesday.

There are at least 252 chemical factories in Pasir Gudang.

Mr Mohd Khuzzan said the authorities were still baffled by what was causing students in Pasir Gudang to experience vomiting and dizziness despite some of the detectors showing no toxic chemicals in the air.

He said the 85 detection teams deployed at the affected schools on Monday found no major chemicals in the air.

"In some schools it was zero, but there were still cases of students with the symptoms. Even all the urine and blood samples taken from the students have turned out to be negative," he said.

"However, we will still continue the detection at the 85 schools," he said, adding that some of the students were affected more than once.

Mr Mohd Khuzzan said on Monday that a total of 310 students and three teachers from 31 schools had the symptoms. Out of that number, 127 were sent to nearby clinics and three were warded.

He said the Health Ministry was continuing to provide psychological support at the schools involved.

Mr Mohd Khuzzan added that all 111 schools in Pasir Gudang would be adopted by the chemical factories as part of their corporate social responsibility activities and would be equipped with a gas detector.

Police will continue to man four roadblocks that have been set up around Pasir Gudang. Seri Alam officer-in-charge Superintendent Ismail Dollah said 60 officers from four police stations have been assigned to man the roadblocks.

"The roadblocks are to monitor and prevent any attempts by irresponsible industries or individuals to transfer materials that can harm public safety," he said.

This is not the first time Pasir Gudang has been hit with pollution. In March, 111 primary and secondary schools in Pasir Gudang were shut for two weeks following the illegal dumping of chemicals into Sungai Kim Kim, which flows into the Strait of Johor just north of Singapore's Pulau Ubin.

More than 5,800 people sought medical treatment after inhaling toxic fumes from the river.

Johor ruler Sultan Ibrahim Sultan Iskandar said last week he would propose to the Johor government to "get rid of or relocate" industries that had negative environmental impact on the state, saying that "they endangered not only just the people of Johor but also Singaporeans".