Environment Minister Gopal Rai on Sunday said that although the air quality in Delhi has shown improvement in the past two days, people should remain vigilant and adhere to pollution control measures.

Rai also recalled that the progress made just before Diwali due to rain and favourable meteorological conditions was compromised by people bursting firecrackers.

"Despite the recent improvements, it's crucial to stay cautious and follow all air pollution control measures," the minister told reporters.

Delhi and its suburbs witnessed a further improvement in air quality on Sunday, attributed primarily to favourable atmospheric conditions such as wind direction and speed.

At 7 am, the city's Air Quality Index (AQI) stood at 290. The 24-hour average AQI was 319 on Saturday, 405 on Friday and 419 on Thursday.

An AQI between zero and 50 is considered 'good', 51 and 100 'satisfactory', 101 and 200 'moderate', 201 and 300 'poor', 301 and 400 'very poor', 401 and 450 'severe', and above 450 'severe plus'.

The Centre lifted stringent restrictions on Saturday, including a ban on certain construction activities and the entry of polluting trucks into Delhi, given the decline in air pollution levels.

These measures are part of Stage IV of the Centre's air pollution control plan -- Graded Response Action Plan (GRAP).

The Commission for Air Quality Management (CAQM) in National Capital Region and Adjoining Areas, a statutory body responsible for formulating strategies to combat pollution, asked Delhi and NCR states to revoke emergency measures which allowed only CNG, electric and BS VI-compliant vehicles to enter Delhi from other states, except those in essential services.

Under Stage IV of GRAP, all non-essential medium and heavy goods vehicles were prohibited in the capital.

Rai confirmed that other restrictions under stages I, II, and III of GRAP, including a ban on non-essential construction, mining, stone crushers and diesel generators will continue.

The ban on BS III petrol and BS IV diesel vehicles will also continue, he said.

"We will reassess these restrictions if the situation continues to improve," the minister said.

The air quality predictions by the India Meteorological Department and the Indian Institute of Tropical Meteorology suggest no significant deterioration in the overall air quality of Delhi-NCR in the upcoming days, according to the CAQM.

Except for the headline, this story has not been edited by The Telegraph Online staff and has been published from a syndicated feed.