A thick blanket of smog engulfed New Delhi, the Indian capital, following Diwali celebrations over the weekend during which people set off huge quantities of fireworks.

Delhi, which is already considered among the most polluted cities in the world by World Health Organization, has been struggling with bad air quality. In an interview with AFP, Gufran Beig, India’s chief scientist at the System of Air Quality Weather Forecasting and Research, said pollutants in Delhi air rose nearly 10 times above the normal level on Monday. “Almost 60-70% of the smoke came from the firecrackers,” he said.