Delhi's air quality showed a slight improvement on Friday with increased wind speed but remained in the 'very poor' category, authorities said.
According to the Central Pollution Control Board (CPCB) data, the overall Air Quality Index (AQI) in the city reached 385, which is in the 'very poor' category.
Seventeen areas in Delhi recorded 'severe' air quality, while 12 gauged 'very poor' air quality, it said.
Ghaziabad recorded 'severe' air quality while Faridabad, Gurgaon and Noida recorded 'very poor' air quality.
The overall PM2.5 level (fine particulate matter in the air with a diameter of less than 2.5 micrometers) in Delhi was recorded at 228 while the PM10 level was at 358, the CPCB said.
An AQI between 100 and 200 comes under 'moderate' category, 201 and 300 is considered 'poor', 301 and 400 'very poor', while that between 401 and 500 is 'severe'.
In view of the air quality in Delhi, the Supreme Court-appointed Environment Pollution Control Authority (EPCA) ordered a 24-hour ban on the entry of trucks into the national capital.
The entry of trucks to Delhi would be disallowed "from 11 pm on Friday to 11 pm on Saturday in view of the severe pollution in the city, the EPCA instructed authorities.
In a letter to the chief secretaries of Delhi and the neighbouring states of Uttar Pradesh and Haryana, EPCA chief Bhure Lal directed them to stop the entry of truck traffic into the national capital (except essential commodities) during the period.
This would be a second time this season that a ban on the entry of trucks would be imposed.
Earlier, it was done in November when the deterioration of air quality was observed.
Delhi's air quality was in the 'very poor' category on Tuesday, before deteriorating to 'severe' on Wednesday as it was on Monday.
The Centre-run System of Air Quality and Weather Forecasting (SAFAR) said other than surface wind speed, all the rest meteorological factors are likely to be "unfavourable".