The air quality in Kolkata deteriorated on Monday night as the city choked under a thick smoke due to bursting of firecrackers amid Diwali and Kali Puja celebrations.

As part of their crackdown to curb different violations during the festivities, nearly 850 kilograms of banned firecrackers and 68.4 litres of liquor were seized during raids carried out on Monday night across the city, the Kolkata Police said.

A total of 640 people were arrested for various offences, including 183 people for bursting banned firecrackers, they added. They also claimed to have detained 451 people for “disorderly behaviour”, and six persons for gambling.

According to the West Bengal Pollution Control Board (WBPCB), the AQI was 186 (PM 2.5) at Victoria Memorial, 364 at Belur in Howrah, and 361 at Padmapukur. In Kolkata’s Ballygunge, the AQI touched 173, while it was 169 at Jadavpur and 167 at Rabindra Bharati University in north Kolkata’s Sinthi area at 10 pm.

The WBPCB had permitted only eco-friendly green crackers between 8 pm and 10 pm on Monday night. However, reports came in of high-decibel fireworks being burst in several areas, including Bidhannagar, Behala, and Maniktala.

Kolkata Police Commissioner Manoj Kumar Verma told mediapersons, “It is allowed till 90 decibel but is illegal beyond that. We received complaints and have made several arrests.”

Traffic authorities also issued challns against 882 offenders for violations such as not wearing helmets while riding pillion, bursting firecrackers in restricted zones, rash driving, and public disorder. Ninety-nine motorists were booked for drunk driving, while 156 faced penalties for violating other traffic and safety rules.

Residents, however, alleged that violations continued unchecked.

Priya Mallick, a resident of Bidhannagar, said, “Firecrackers were burst since Dhanteras. Banned firecrackers are being used and not a single police patrol was seen. We have senior citizens but no heed was paid to that.”

Srinanda Chakrabarty of Tollygunge said, “My mother has asthma. Yesterday, unlike any other year, illegal firecrackers were burst till the early hours, and my mother had difficulty breathing.”

On Sunday, the Air Quality Index (AQI) in Kolkata ranged between ‘unhealthy’ and ‘poor’. But on Monday, it worsened in Kolkata and Howrah, as firecrackers were burst beyond the permissible hours.

At 8 pm on Monday, the AQI was relatively lower — 164 at Victoria, 159 at Jadavpur, 117 at Fort William, 161 at Belur Math, 102 at Rabindra Bharati University, and 134 at Ballygunge.

Police had issued warnings that strict action would be taken against anyone violating the state’s green fireworks directive.