Delhi has been battling alarming pollution levels since October. (Representational Image)

Even as the national capital continued its battle with toxic air, several instances of firecracker bursting, before and after the time limit fixed by the top court, were observed in Delhi-NCR during New Year celebrations.

The Centre-run System of Air Quality and Weather Forecasting (SAFAR) on Monday warned that any new trigger, particularly due to "open fire and pyrotechnic display (firecrackers)", will make the air heavier and thicker which may lead to rapid deterioration in air quality to severe-plus range.

The Central Pollution Control Board (CPCB) had written to Delhi police and district magistrates of the national capital, Noida and Gurgaon ahead of Christmas and New Year's eve to ensure that the Supreme court order in this regard is followed and no firecrackers are burst.

But despite the warnings, several instances of violations of the apex court order was observed, officials said, adding the number of violations committed was, however, not available immediately.

The Supreme Court had said on Christmas and the New Year's eve, green firecrackers would be allowed to be burst between 11.55 pm and 12.30 am, since these celebrations start midnight.

Delhi has been battling alarming pollution levels since October, and in the last 10 days, the national capital witnessed long spells of severe air quality which continued to plague the city on New Year's eve and on the first day of January.

The SAFAR has said, "Any new trigger in terms of additional local emission, particularly from open fire, pyrotechnic display (fire crackers) and fossil fuel burning, may make the air heavier, thicker, and with low ventilation it may lead to rapid deterioration in the quality of air to severe-plus range."