A bench headed by NGT Chairperson Justice Swatanter Kumar issued warrants against around 25 hookah bars which were asked to file their response before it.
During the hearing, the green panel asked the authorities to strictly regulate these restaurants and bars and warned that it would order their closure in case of any environmental pollution.
The matter has been listed for final hearing on December 4.
Responding to the developments in the tribunal, BJP MLA Manjinder Singh Sirsa, who has filed a plea in NGT against hookah bars, said that it was tragic that the AAP government led by Arvind Kejriwal "was not ready to awake from deep slumber whereas thousands of city youth are becoming addicted to drugs due to hookah smoking which is far more dangerous than the smoking of cigarettes".
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Sirsa had contended that the ambient air quality standards in public places such as restaurants and bars were dangerously higher than the prescribed norms.
Referring to the Prohibition of Smoking in Public Places Rules 2008, the plea said these rules are being openly flouted by various restaurants and hookah bars in Delhi wherein hookah, as a tobacco product, is being permitted to be smoked in open spaces without designating any part of its premises as a smoking area.
Sirsa had earlier alleged that hookah bars were "ruining" the youth of Delhi by turning them into "drug addicts".
"Despite launch of a campaign in the country to contain use of tobacco and ban hookah bars, most hookah bars in Delhi are running on restaurant licences illegally and selling products that are harmful for the youth," he had earlier said.