Energy, Science, Technology, Environment and Climate Change Minister Yeo Bee Yin on Friday said the authorities are still trying to determine the exact cause of the chemical pollution in Pasir Gudang, Johor.
However, the minister said air quality readings found high amounts of methyl mercaptan gas in the area, and regarded that as an anomaly since it could cause averse effects on children as well as those with health conditions like asthma.
Also detected in Pasir Gudang was acrylonitrile and acrolein gases but Yeo said the three gases were not detected in the blood samples of the victims.

Health Minister Datuk Seri Dr Dzulkefly Ahmad, who was also present at the press conference, said as of June 27, a total of 748 cases of breathing difficulties were reported in Pasir Gudang, with 709 treated as outpatients while 39 required hospitalisation.

Read more at https://www.thestar.com.my/news/nation/2019/06/28/three-types-of-gases-detected-in-pasir-gudang-during-air-disaster/