PETALING JAYA (THE STAR/ASIA NEWS NETWORK) - Malaysia's Health Ministry has ruled out pigeon droppings as a contaminant that caused vomiting and breathing difficulty among pupils at a school in Johor's Pasir Gudang district.

Minister Dzulkefly Ahmad said his ministry, together with the Energy, Science, Technology, Environment and Climate Change Ministry, had updated all findings related to toxic air pollution in the industrial area and come up with an analysis.

"Until today, we have not found (any relation to bird droppings). We will keep monitoring the situation closely," he said on Thursday (July 25).

At the same time, Datuk Seri Dzulkefly also said the ministry has engaged an independent committee comprised of experts to conduct a similar investigation.

"We will compare their findings with ours later," he said, adding that the committee's report is expected to be wrapped up by this month.

The minister was commenting on the remark by Johor Health, Culture and Heritage Committee chairman Mohd Khuzzan Abu Bakar on Tuesday that the state government was not ruling out the possibility that contamination from bird droppings had caused several episodes of vomiting and breathing difficulty among pupils of SK Tanjung Puteri Resort.

The primary school was among the 475 educational institutions in Pasir Gudang that were closed for three days last month after more than 100 students from over 30 schools experienced symptoms like nausea and dizziness.

These were attributed to "toxic fumes", the cause of which has not been pinpointed.

When the schools reopened, many students and teachers again experienced similar symptoms and were rushed to clinics.

However, pollution detectors showed no toxic chemicals in the air.

That was not the first time Pasir Gudang has been hit by pollution.

In March, 111 primary and secondary schools in the area 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 has said he will propose to the Johor government to "get rid of or relocate" industries that have a negative environmental impact on the state, adding that "they endangered not just the people of Johor but also Singaporeans".