NEW DELHI: Delhi Environment Minister Gopal Rai on Saturday asked all departments concerned to reactivate their teams for effective implementation of curbs under Stage 3 of the Centre's air pollution control plan.

Addressing a press conference here, the minister said that air quality in Delhi deteriorated from very poor to the severe category on Friday due to low temperatures and calm winds.

"Given worsening air quality, the Commission for Air Quality Management re-invoked curbs under Stage 3 of the Graded Response Action Plan (GRAP). This means a ban on non-essential construction work and plying of BS-III petrol and BS-IV diesel four-wheelers in Delhi-NCR," he said.

On Saturday morning, the air quality index in Delhi was recorded at 447, which comes under the 'severe' category, according to the Central Pollution Control Board (CPCB. The minister said the government has alerted all 28 departments involved in pollution control efforts.

"They have been asked to reactivate their teams to manage the situation at the earliest," he said.

Rai said non-essential construction work, stone crushing and mining will remain banned in Delhi until further orders.

Construction work related to national security or defence, projects of national importance, healthcare, railways, metro rail, airports, interstate bus terminals, highways, roads, flyovers, overbridges, power transmission, pipelines, sanitation and water supply are exempted from the ban.

Under Stage 3, the plying of BS-III petrol and BS-IV diesel four-wheelers in the national capital will also be restricted.

The GRAP is the Centre's air pollution control plan implemented in the region during the winter season.

It categorises actions into four stages: Stage-1 - 'Poor' (AQI 201-300); Stage-2 - 'Very Poor' (AQI 301-400); Stage-3 - 'Severe' (AQI 401-450); and Stage-4 - 'Severe Plus' (AQI>450).