NEW DELHI: Delhi recorded its worst air quality of the year the morning after Diwali as the pollution level entered "severe-plus emergency" category due to rampant bursting of toxic firecrackers , authorities said Thursday.In a gross violation of a Supreme Court order , people in several cities burst firecrackers until at least midnight, two hours after the 10 pm deadline. Loud bangs rent the air in New Delhi. Violations were also recorded in Mumbai, Kolkata, Jaipur and other major cities.Partly as a result of smoke from the firecrackers, the overall air quality index (AQI) in Delhi jumped to 574 which falls in the "severe-plus emergency" category, according to data by the Centre-run SAFAR (System of Air Quality and Weather Forecasting And Research).The overall AQI was ten times the permissable limit. An AQI between 0 and 50 is considered "good", 51 and 100 "satisfactory", 101 and 200 "moderate", 201 and 300 "poor", 301 and 400 "very poor", and 401 and 500 "severe". AQI above 500 falls in the "severe-plus emergency" category.The sharp spike in pollution is caused by rampant burning of firecrackers that has led to the formation of a smoky layer across the national capital and drastically reduced visibility, the authorities said.The SAFAR had warned that even if partial toxic firecrackers as compared to last year were burnt, then the air quality would fall in the "severe" category.Delhi's AQI is around 574 at present. Air Quality Index entered the "severe" category at 2 am after midnight on Thursday and will continue to remain in the "severe" category until evening, a senior official said.The PM2.5 (particles in the air with a diameter of less than 2.5 micrometres) level was recorded nearly seven times the permissable limit at 414. The PM10 (particles in the air with a diameter of less than 10 micrometres) level was recorded four times the permissable limit at 433.India's official permissible PM2.5 limit is 60 µgm-3 while PM10 level is 100 µgm-3.The ultra fine particulate materials PM2.5 and PM10 in the air pose health hazards as they can enter the respiratory system and reach the bloodstream.Six areas in Delhi recorded "severe" air quality while 27 areas recorded "very poor" quality air, according to data of the Central Pollution Control Board.A "severe plus emergency" AQI essentially means that even healthy people may suffer from respiratory illnesses on prolonged exposure. This air will seriously affect those with ailments, according to the advisory issued by SAFAR.The Supreme Court has allowed people to burst firecrackers from 8 pm to 10 pm only on Diwali and other festivals. The top court also allowed manufacture and sale of just "green crackers" which have low emission of light, sound and harmful chemicals.The court said the police should ensure that there was no sale of banned firecrackers and in case of any violation, the Station House Officer (SHO) of the police station of the area would be held personally liable and this would amount to committing contempt of the court.But despite the Supreme Court's order, certain places recorded violations where firecrackers were burnt before and after the set time frame.The areas where the violations were recorded included Mayur Vihar Extension, Lajpat Nagar, Lutyens' Delhi, IP extension, Dwarka and Noida Sector 78.The police admitted that violations were observed and it would take serious legal action against the people violating the apex court order. They said they were continuously patrolling the areas to check for violations.