This is the second serious incident involving poisonous gas in the district in the past three months.
Johor chief minister Sahruddin Jamal said 75 people had so far been sent to hospital for treatment, according to official news agency Bernama.
Authorities have now ordered the closure of all 475 educational institutions in the area until June 27, including three institutes of higher education, 111 public schools, 14 private schools and 347 kindergartens.
Prime Minister Mahathir Mohamad said that authorized agencies are conducting investigations over 30 chemical companies in Johor state. He vowed to act against those responsible.
In March, thousands of people in the district were hospitalized when waste was dumped in a river and emitted noxious fumes.
